Apparatus and method for transdermal delivery of parathyroid hormone agents

ABSTRACT

An apparatus and method for transdermally delivering a biologically active agent comprising a delivery system having a microprojection member (or system) that includes a plurality of microprojections (or array thereof) that are adapted to pierce through the stratum corneum into the underlying epidermis layer, or epidermis and dermis layers. In one embodiment, the PTH-based agent is contained in a biocompatible coating that is applied to the microprojection member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 11/084,634, filed Mar.18, 2005, and claims the benefit of U.S. Provisional Application No.60/571,304, filed May 13, 2004, U.S. Provisional Application No.60/585,276, filed Jul. 1, 2004 and U.S. Provisional Application No.60/643,660, filed Jan. 12, 2005. The contents of each of theseapplications is incorporated herein by reference in their entirety.

FIELD OF THE PRESENT INVENTION

The present invention relates generally to transdermal agent deliverysystems and methods. More particularly, the invention relates to anapparatus and method for transdermal delivery of parathyroid hormoneagents.

BACKGROUND OF THE INVENTION

Active agents (or drugs) are most conventionally administered eitherorally or by injection. Unfortunately, many active agent are completelyineffective or have radically reduced efficacy when orally administered,since they either are not absorbed or are adversely affected beforeentering the bloodstream and thus do not possess the desired activity.On the other hand, the direct injection of the agent intravenously orsubcutaneously, while assuring no modification of the agent duringadministration, is a difficult, inconvenient, painful and uncomfortableprocedure that sometimes results in poor patient compliance.

Hence, in principle, transdermal delivery provides for a method ofadministering active agents that would otherwise need to be deliveredvia hypodermic injection or intravenous infusion. The word“transdermal”, as used herein, is generic term that refers to deliveryof an active agent (e.g., a therapeutic agent, such as a drug or animmunologically active agent, such as a vaccine) through the skin to thelocal tissue or systemic circulatory system without substantial cuttingor penetration of the skin, such as cutting with a surgical knife orpiercing the skin with a hypodermic needle. Transdermal agent deliveryincludes delivery via passive diffusion as well as delivery based uponexternal energy sources, such as electricity (e.g., iontophoresis) andultrasound (e.g., phonophoresis).

Passive transdermal agent delivery systems, which are more common,typically include a drug reservoir that contains a high concentration ofan active agent. The reservoir is adapted to contact the skin, whichenables the agent to diffuse through the skin and into the body tissuesor bloodstream of a patient.

As is well known in the art, the transdermal drug flux is dependent uponthe condition of the skin, the size and physical/chemical properties ofthe drug molecule, and the concentration gradient across the skin.Because of the low permeability of the skin to many drugs, transdermaldelivery has had limited applications. This low permeability isattributed primarily to the stratum corneum, the outermost skin layerwhich consists of flat, dead cells filled with keratin fibers (i.e.,keratinocytes) surrounded by lipid bilayers. This highly-orderedstructure of the lipid bilayers confers a relatively impermeablecharacter to the stratum corneum.

One common method of increasing the passive transdermal diffusionalagent flux involves pre-treating the skin with, or co-delivering withthe agent, a skin permeation enhancer. A permeation enhancer, whenapplied to a body surface through which the agent is delivered, enhancesthe flux of the agent therethrough. However, the efficacy of thesemethods in enhancing transdermal protein flux has been limited, at leastfor the larger proteins, due to their size.

There also have been many techniques and devices developed tomechanically penetrate or disrupt the outermost skin layers therebycreating pathways into the skin in order to enhance the amount of agentbeing transdermally delivered. Illustrative is the drug delivery devicedisclosed in U.S. Pat. No. 3,964,482.

Other systems and apparatus that employ tiny skin piercing elements toenhance transdermal agent delivery are disclosed in U.S. Pat. Nos.5,879,326, 3,814,097, 5,250,023, 3,964,482, Reissue No. 25,637, and PCTPublication Nos. WO 96/37155, WO 96/37256, WO 96/17648, WO 97/03718, WO98/11937, WO 98/00193, WO 97/48440, WO 97/48441, WO 97/48442, WO98/00193, WO 99/64580, WO 98/28037, WO 98/29298, and WO 98/29365; allincorporated herein by reference in their entirety.

The disclosed systems and apparatus employ piercing elements of variousshapes and sizes to pierce the outermost layer (i.e., the stratumcorneum) of the skin. The piercing elements disclosed in thesereferences generally extend perpendicularly from a thin, flat member,such as a pad or sheet. The piercing elements in some of these devicesare extremely small, some having a microprojection length of only about25-400 microns and a microprojection thickness of only about 5-50microns. These tiny piercing/cutting elements make correspondingly smallmicroslits/microcuts in the stratum corneum for enhancing transdermalagent delivery therethrough.

The disclosed systems further typically include a reservoir for holdingthe agent and also a delivery system to transfer the agent from thereservoir through the stratum corneum, such as by hollow tines of thedevice itself. One example of such a device is disclosed in WO 93/17754,which has a liquid agent reservoir. The reservoir must, however, bepressurized to force the liquid agent through the tiny tubular elementsand into the skin. Disadvantages of such devices include the addedcomplication and expense for adding a pressurizable liquid reservoir andcomplications due to the presence of a pressure-driven delivery system.

As disclosed in U.S. patent application Ser. No. 10/045,842, which isfully incorporated by reference herein, it is possible to have theactive agent that is to be delivered coated on the microprojectionsinstead of contained in a physical reservoir. This eliminates thenecessity of a separate physical reservoir and developing an agentformulation or composition specifically for the reservoir.

As is well known in the art, osteoporosis is a bone disordercharacterized by progressive bone loss that predisposes an individual toan increased risk of fracture, typically in the hip, spine and wrist.The progressive bone loss, which typically begins between the ages of 30and 40, is mainly asymptomatic until a bone fracture occurs, leading toa high degree of patient morbidity and mortality. Eighty percent ofthose affected by osteoporosis are women and, based on recent studies,during the six years following the onset of menopause, women lose onethird of their bone mass.

As is also well known in the art, parathyroid hormone (PTH) is a hormonesecreted by the parathyroid gland that regulates the metabolism ofcalcium and phosphate in the body. PTH has stirred great interest in thetreatment of osteoporosis for its ability to promote bone formation and,hence, dramatically reduced incidence of fractures. Large-scale clinicaltrials have shown that PTH effectively and safely reduces the percentageof vertebral and non-vertebral fractures in women with osteoporosis.

PTH-based agents have also stirred interest in the treatment of bonefractures (in both men and women) by virtue of their ability toaccelerate bone healing.

To this end, various stabilized formulations of PTH-based agents havebeen developed that can be reconstituted for subcutaneous injection,which, as discussed below, is the conventional means of delivery.Illustrative are the formulations disclosed in U.S. Pat. No. 5,563,122(“Stabilized Parathyroid Hormone Composition”) and U.S. PatentApplication Pub. No. 2002/0107200 (“Stabilized Teriparatide Solutions”),which are incorporated by reference herein in their entirety.

A currently approved injectable PTH-based agent is FORTEO™ (an rDNAderived teriparatide injection), which contains recombinant humanparathyroid hormone (1-34), (rhPTH (1-34)). FORTEO™ is typicallyprescribed for women with a history of osteoporotic fracture, who havemultiple risk factors for fracture, or who have failed or are intolerantof previous osteoporosis therapy, based on a physician's assessment. Inpostmenopausal women with osteoporosis, FORTEO™ has been found toincrease bone mineral density (BMD) and reduce the risk of vertebral andnon-vertebral fractures.

FORTEO™ has also been found to increase bone mass in men with primary orhypogonadal osteoporosis who are at high risk for fracture. Theseinclude men with a history of osteoporotic fracture, or who havemultiple risk factors for fracture, or who have failed or are intolerantto previous osteoporosis therapy. In men with primary or hypogonadalosteoporosis, FORTEO™ has similarly been found to increase BMD.

In addition to subcutaneous injection, other means of deliveringPTH-based agents have also been investigated. For example, variouspulmonary delivery (i.e., inhalation) methods are discussed in“Pulmonary Delivery of Drugs for Bone Disorders,” Advanced Drug DeliveryReviews, Vol. 42, Issue 3, pp. 239-248 (Aug. 31, 2000), Patton,“Bioavailability of Pulmonary Delivered Peptides and Proteins:—Interferon, Calcitonins and Parathyroid Hormones,” Journal ofControlled Release, Vol. 28, Issues 1-3, pp. 79-85 (January 1994),Patton, et al., “Impact of Formulation and Methods of Pulmonary Deliveryon Absorption of Parathyroid Hormone (1-34) from Rat Lungs,” Journal ofPharmaceutical Sciences, Vol. 93, Issue 5, pp. 1241-1252 (May 2004),Codrons, et al., “Systemic Delivery of Parathyroid Hormone (1-34) UsingInhalation Dry Powders in Rats,” Journal of Pharmaceutical Sciences,Vol. 92, Issue 5, pp. 938-950 (May 2003) and Pfützner, A, et al., “PilotStudy with Technosphere/PTH (1-34)—A New Approach for EffectivePulmonary Delivery of Parathyroid Hormone (1-34)”, Horm. Metab. Res.,Vol. 35(5), pp. 319-23.

Various methods of active transdermal delivery of PTH-based agents arealso discussed in “The Effect of Electroporation on EontophoreticEransdermal Delivery of Calcium Regulating Hormones,” Journal ofControlled Release, Vol. 66, Issues 2-3, pp. 127-133 (May 15, 2000) andChang, et al., “Prevention of Bone Loss in Ovariectomized Rats byPulsatile Transdermal Iontophoretic Administration of Human PTH (1-34),”Journal of Pharmaceutical Sciences, Vol. 91, Issue 2, pp. 350-361(February 2002).

Despite the efficacy of PTH in treating disorders such as osteoporosis,there are several drawbacks and disadvantages associated with thedisclosed prior art methods of delivering PTH, particularly, viasubcutaneous injection. A major drawback is that subcutaneous injectionis a difficult and uncomfortable procedure, which often results in poorpatient compliance.

Intracutaneous administration of agents, such as hGH, usingmicroprojection systems has previously been documented to provide apharmacokinetic profile of hGH similar to that observed followingsubcutaneous administration. See, e.g., Cormier, et al., U.S. PatentApplication Pub. No. 2002/0128599, entitled “Transdermal Drug DeliveryDevices Having Coated Microprotrusions”.

Continuous infusion of a PTH-based agent in vivo results in active boneresorption. It is therefore of critical importance that the PTH-basedagent be administered in a pulsatile fashion. Based on the efficacyresults from the once daily subcutaneous injection, any alternativeroute of PTH delivery should provide blood concentration of PTH noslower than that for subcutaneously injected PTH.

It would thus be desirable to provide an agent delivery system thatfacilitates minimally invasive administration of PTH-based agents. Itwould further be desirable to provide an agent delivery system thatprovides a pharmacokinetic profile of the PTH-based agent similar tothat observed following subcutaneous administration.

It is therefore an object of the present invention to provide atransdermal agent delivery apparatus and method that providesintracutaneous delivery of a PTH-based agent to a patient.

It is another object of the invention to provide a transdermal agentdelivery apparatus and method that provides a pharmacokinetic profile ofthe PTH-based agent similar to or fatter than that observed followingsubcutaneous administration.

It is another object of the invention to provide a transdermal agentdelivery apparatus and method that provides pharmacologically activeblood concentration of a PTH-based agent for a period of up to eighthours.

It is another object of the invention to provide a PTH-based agentformulation for intracutaneous delivery to a patient.

It is another object of the present invention to provide a transdermalagent delivery apparatus and method that includes microprojectionscoated with a biocompatible coating that includes at least onebiologically active agent, preferably, a PTH-based agent.

SUMMARY OF THE INVENTION

In accordance with the above objects and those that will be mentionedand will become apparent below, the apparatus and method fortransdermally delivering a PTH-based agent in accordance with thisinvention generally comprises a delivery system having a microprojectionmember (or system) that includes a plurality of microprojections (orarray thereof) that are adapted to pierce through the stratum corneuminto the underlying epidermis layer, or epidermis and dermis layers. Ina preferred embodiment, the microprojection member includes abiocompatible coating having at least one PTH-based agent disposedtherein.

In one embodiment of the invention, the microprojection member has amicroprojection density of at least approximately 10microprojections/cm², more preferably, in the range of at leastapproximately 200-2000 microprojection/cm².

In one embodiment, the microprojection member is constructed out ofstainless steel, titanium, nickel titanium alloys, or similarbiocompatible materials.

In another embodiment, the microprojection member is constructed out ofa non-conductive material, such as a polymeric material. Alternatively,the microprojection member can be coated with a non-conductive material,such as Parylene®, or a hydrophobic material, such as Teflon®, siliconor other low energy material.

The coating formulations applied to the microprojection member to formsolid biocompatible coatings can comprise aqueous and non-aqueousformulations. Preferably, the coating formulations include at least onePTH-based agent, which can be dissolved within a biocompatible carrieror suspended within the carrier.

In a preferred embodiment, the PTH-based agent is selected from thegroup consisting of hPTH (1-34), hPTH salts and analogs, teriparatideand related peptides. Throughout this application, the terms “PTH-basedagent” and “hPTH (1-34) agent” include, without limitation, recombinanthPTH (1-34), synthetic hPTH (1-34), PTH (1-34), teriparatide, hPTH(1-34) salts, simple derivatives of hPTH (1-34), such as hPTH (1-34)amide, and closely related molecules, such as hPTH (1-33) or hPTH (1-31)amide, or any other closely related osteogenic peptide. Synthetic hPTH(1-34) is the most preferred PTH agent.

Examples of pharmaceutically acceptable hPTH salts include, withoutlimitation, acetate, propionate, butyrate, pentanoate, hexanoate,heptanoate, levulinate, chloride, bromide, citrate, succinate, maleate,glycolate, gluconate, glucuronate, 3-hydroxyisobutyrate,tricarballylicate, malonate, adipate, citraconate, glutarate, itaconate,mesaconate, citramalate, dimethylolpropinate, tiglicate, glycerate,methacrylate, isocrotonate, β-hydroxibutyrate, crotonate, angelate,hydracrylate, ascorbate, aspartate, glutamate, 2-hydroxyisobutyrate,lactate, malate, pyruvate, fumarate, tartarate, nitrate, phosphate,benzene, sulfonate, methane sulfonate, sulfate and sulfonate.

Preferably, the PTH-based agent is present in the coating formulation ata concentration in the range of approximately 1-30 wt. %.

More preferably, the amount of PTH-based agent contained in the solidbiocompatible coating (i.e., microprojection member or product) is inthe range of approximately 1 μg-1000 μg, even more preferably, in therange of approximately 10-100 μg.

Also preferably, the pH of the coating formulation is belowapproximately pH 6. More preferably, the coating formulation has a pH inthe range of approximately pH 2-pH 6. Even more preferably, the coatingformulation has a pH in the range of approximately pH 3-pH 6.

In certain embodiments of the invention, the viscosity of the coatingformulation that is employed to coat the microprojections is enhanced byadding low volatility counterions. In one embodiment, the PTH-basedagent has a positive charge at the formulation pH and theviscosity-enhancing counterion comprises an acid having at least twoacidic pKas. Suitable acids include maleic acid, malic acid, malonicacid, tartaric acid, adipic acid, citraconic acid, fumaric acid,glutaric acid, itaconic acid, meglutol, mesaconic acid, succinic acid,citramalic acid, tartronic acid, citric acid, tricarballylic acid,ethylenediaminetetraacetic acid, aspartic acid, glutamic acid, carbonicacid, sulfuric acid and phosphoric acid.

Another preferred embodiment is directed to a viscosity-enhancingmixture of counterions, wherein the PTH-based agent has a positivecharge at the formulation pH and at least one of the counterioncomprises an acid having at least two acidic pKas. The other counterioncomprises an acid with one or more pKas. Examples of suitable acidsinclude hydrochloric acid, hydrobromic acid, nitric acid, sulfuric acid,maleic acid, phosphoric acid, benzene sulfonic acid, methane sulfonicacid, citric acid, succinic acid, glycolic acid, gluconic acid,glucuronic acid, lactic acid, malic acid, pyruvic acid, tartaric acid,tartronic acid, fumaric acid, acetic acid, propionic acid, pentanoicacid, carbonic acid, malonic acid, adipic acid, citraconic acid,levulinic acid, glutaric acid, itaconic acid, meglutol, mesaconic acid,citramalic acid, citric acid, aspartic acid, glutamic acid,tricarballylic acid and ethylenediaminetetraacetic acid.

In the noted embodiments of the invention, the amount of counterion ispreferably sufficient to neutralize the charge of the PTH. In suchembodiments, the amount of the counterion or mixture of counterions ispreferably sufficient to neutralize the charge present on the agent atthe pH of the formulation. In additional embodiments, excess counterion(as the free acid or as a salt) is added to the peptide to control pHand provide adequate buffering capacity.

In another preferred embodiment, the agent comprises hPTH (1-34) and thecounterion comprises a viscosity-enhancing mixture of counterions chosenfrom the group consisting of citric acid, tartaric acid, malic acid,hydrochloric acid, glycolic acid and acetic acid. Preferably, thecounterions are added to the formulation to achieve a viscosity in therange of approximately 20-200 cp.

In a preferred embodiment of the invention, the viscosity-enhancingcounterion comprises an acidic counterion, such as a low volatility weakacid that exhibits at least one acidic pKa and a melting point higherthan about 50° C. or a boiling point higher than about 170° C. atP_(atm). Examples of such acids include citric acid, succinic acid,glycolic acid, gluconic acid, glucuronic acid, lactic acid, malic acid,pyruvic acid, tartaric acid, tartronic acid, and fumaric acid.

In another preferred embodiment, the counterion comprises a strong acidthat exhibits at least one pKa lower than about 2. Examples of suchacids include hydrochloric acid, hydrobromic acid, nitric acid, sulfonicacid, sulfuric acid, maleic acid, phosphoric acid, benzene sulfonic acidand methane sulfonic acid.

Another preferred embodiment is directed to a mixture of counterions,wherein at least one of the counterion comprises a strong acid and atleast one of the counterion comprises a low volatility weak acid.

Another preferred embodiment is directed to a mixture of counterions,wherein at least one of the counterion comprises a strong acid and atleast one of the counterion comprises a weak acid having a highvolatility and exhibiting at least one pKa higher than about 2 and amelting point lower than about 50° C. or a boiling point lower thanabout 170° C. at P_(atm). Examples of such acids include acetic acid,propionic acid, pentanoic acid and the like.

The acidic counterion is preferably present in an amount that issufficient to neutralize the positive charge present on the PTH-basedagent at the pH of the formulation. In an additional embodiment, anexcess counterion (as the free acid or as a salt) is added to control pHand to provide adequate buffering capacity.

In another embodiment of the invention, the coating formulation includesat least one buffer. Examples of such buffers include, withoutlimitation, ascorbic acid, citric acid, succinic acid, glycolic acid,gluconic acid, glucuronic acid, lactic acid, malic acid, pyruvic acid,tartaric acid, tartronic acid, fumaric acid, maleic acid, phosphoricacid, tricarballylic acid, malonic acid, adipic acid, citraconic acid,glutaratic acid, itaconic acid, mesaconic acid, citramalic acid,dimethylolpropionic acid, tiglic acid, glyceric acid, methacrylic acid,isocrotonic acid, β-hydroxybutyric acid, crotonic acid, angelic acid,hydracrylic acid, aspartic acid, glutamic acid, glycine and mixturesthereof.

In one embodiment of the invention, the coating formulation includes atleast one antioxidant, which can comprise sequestering agents, suchsodium citrate, citric acid, EDTA (ethylene-dinitrilo-tetraacetic acid)or free radical scavengers, such as ascorbic acid, methionine, sodiumascorbate and the like. Presently preferred antioxidants comprise EDTAand methionine.

In the noted embodiments of the invention, the concentration of theantioxidant is preferably in the range of approximately 0.01-20 wt. % ofthe coating formulation. More preferably, the concentration of theantioxidant is in the range of approximately 0.03-10 wt. % of thecoating formulation.

In one embodiment of the invention, the coating formulation includes atleast one surfactant, which can be zwitterionic, amphoteric, cationic,anionic, or nonionic, including, without limitation, sodiumlauroamphoacetate, sodium dodecyl sulfate (SDS), cetylpyridiniumchloride (CPC), dodecyltrimethyl ammonium chloride (TMAC), benzalkonium,chloride, polysorbates such as Tween 20 and Tween 80, other sorbitanderivatives, such as sorbitan lauratealkoxylated alcohols, such aslaureth-4 and polyoxyethylene castor oil derivatives, such as CremophorEL®.

In the noted embodiments of the invention, the concentration of thesurfactant is preferably in the range of approximately 0.01-20 wt. % ofthe coating formulation. Preferably, the concentration of the surfactantis in the range of approximately 0.05-1 wt. % of the coatingformulation.

In a further embodiment of the invention, the coating formulationincludes at least one polymeric material or polymer that has amphiphilicproperties, which can comprise, without limitation, cellulosederivatives, such as hydroxyethylcellulose (HEC),hydroxypropylmethylcellulose (HPMC), hydroxypropycellulose (HPC),methylcellulose (MC), hydroxyethylmethylcellulose (HEMC), orethylhydroxy-ethylcellulose (EHEC), as well as pluronics.

In one embodiment of the invention, the concentration of the polymerpresenting amphiphilic properties in the coating formulation ispreferably in the range of approximately 0.01-20 wt. %, more preferably,in the range of approximately 0.03-10 wt. % of the coating formulation.

In another embodiment, the coating formulation includes a hydrophilicpolymer selected from the following group: hydroxyethyl starch,carboxymethyl cellulose and salts of, dextran, poly(vinyl alcohol),poly(ethylene oxide), poly(2-hydroxyethyl-methacrylate), poly(n-vinylpyrolidone), polyethylene glycol and mixtures thereof, and likepolymers.

In a preferred embodiment, the concentration of the hydrophilic polymerin the coating formulation is in the range of approximately 1-30 wt. %,more preferably, in the range of approximately 1-20 wt. % of the coatingformulation.

In another embodiment of the invention, the coating formulation includesa biocompatible carrier, which can comprise, without limitation, humanalbumin, bioengineered human albumin, polyglutamic acid, polyasparticacid, polyhistidine, pentosan polysulfate, polyamino acids, sucrose,trehalose, melezitose, raffinose and stachyose.

Preferably, the concentration of the biocompatible carrier in thecoating formulation is in the range of approximately 2-70 wt. %, morepreferably, in the range of approximately 5-50 wt. % of the coatingformulation.

In another embodiment, the coating formulation includes a stabilizingagent, which can comprise, without limitation, a non-reducing sugar, apolysaccharide or a reducing sugar.

Suitable non-reducing sugars for use in the methods and compositions ofthe invention include, for example, sucrose, trehalose, stachyose, orraffinose.

Suitable polysaccharides for use in the methods and compositions of theinvention include, for example, dextran, soluble starch, dextrin, andinsulin.

Suitable reducing sugars for use in the methods and compositions of theinvention include, for example, monosaccharides such as, for example,apiose, arabinose, lyxose, ribose, xylose, digitoxose, fucose,quercitol, quinovose, rhamnose, allose, altrose, fructose, galactose,glucose, gulose, hamamelose, idose, mannose, tagatose, and the like; anddisaccharides such as, for example, primeverose, vicianose, rutinose,scillabiose, cellobiose, gentiobiose, lactose, lactulose, maltose,melibiose, sophorose, and turanose and the like.

Preferably, the concentration of the stabilizing agent in the coatingformulation is at a ratio of approximately 0.1-2.0:1 with respect to thePTH-based agent, more preferably, approximately 0.25-1.0:1 with respectto the PTH-based agent.

In another embodiment, the coating formulation includes avasoconstrictor, which can comprise, without limitation, amidephrine,cafaminol, cyclopentamine, deoxyepinephrine, epinephrine, felypressin,indanazoline, metizoline, midodrine, naphazoline, nordefrin, octodrine,ornipressin, oxymethazoline, phenylephrine, phenylethanolamine,phenylpropanolamine, propylhexedrine, pseudoephedrine, tetrahydrozoline,tramazoline, tuaminoheptane, tymazoline, vasopressin, xylometazoline andthe mixtures thereof. The most preferred vasoconstrictors includeepinephrine, naphazoline, tetrahydrozoline indanazoline, metizoline,tramazoline, tymazoline, oxymetazoline and xylometazoline.

The concentration of the vasoconstrictor, if employed, is preferably inthe range of approximately 0.1 wt. % to 10 wt. % of the coatingformulation.

In another embodiment of the invention, the coating formulation includesat least one “pathway patency modulator”, which can comprise, withoutlimitation, osmotic agents (e.g., sodium chloride), zwitterioniccompounds (e.g., amino acids), and anti-inflammatory agents, such asbetamethasone 21-phosphate disodium salt, triamcinolone acetonide21-disodium phosphate, hydrocortamate hydrochloride, hydrocortisone21-phosphate disodium salt, methylprednisolone 21-phosphate disodiumsalt, methylprednisolone 21-succinate sodium salt, paramethasonedisodium phosphate and prednisolone 21-succinate sodium salt, andanticoagulants, such as citric acid, citrate salts (e.g., sodiumcitrate), dextrin sulfate sodium, aspirin and EDTA.

In yet another embodiment of the invention, the coating formulationincludes a solubilising/complexing agent, which can compriseAlpha-Cyclodextrin, Beta-Cyclodextrin, Gamma-Cyclodextrin,glucosyl-alpha-Cyclodextrin, maltosyl-alpha-Cyclodextrin,glucosyl-beta-Cyclodextrin, maltosyl-beta-Cyclodextrin, hydroxypropylbeta-Cyclodextrin, 2-hydroxypropyl-beta-Cyclodextrin,2-hydroxypropyl-gamma-Cyclodextrin, hydroxyethyl-beta-Cyclodextrin,methyl-beta-Cyclodextrin, sulfobutylether-alpha-Cyclodextrin,sulfobutylether-beta-Cyclodextrin, andsulfobutylether-gamma-Cyclodextrin. Most preferredsolubilising/complexing agents are beta-Cyclodextrin, hydroxypropylbeta-Cyclodextrin, 2-hydroxypropyl-beta-Cyclodextrin andsulfobutylether7 beta-Cyclodextrin.

The concentration of the solubilising/complexing agent, if employed, ispreferably in the range of approximately 1 wt. % to 20 wt. % of thecoating formulation.

In another embodiment of the invention, the coating formulation includesat least one non-aqueous solvent, such as ethanol, isopropanol,methanol, propanol, butanol, propylene glycol, dimethysulfoxide,glycerin, N,N-dimethylformamide and polyethylene glycol 400. Preferably,the non-aqueous solvent is present in the coating formulation in therange of approximately 1 wt. % to 50 wt. % of the coating formulation.

Preferably, the coating formulations have a viscosity less thanapproximately 500 centipoise and greater than 3 centipoise.

In one embodiment of the invention, the thickness of the biocompatiblecoating is less than 25 microns, more preferably, less than 10 microns,as measured from the microprojection surface.

In accordance with one embodiment of the invention, the method fordelivering a PTH-based agent to a subject comprises (i) providing amicroprojection member having a plurality of stratum corneum-piercingmicroprojections, the microprojection member having a biocompatiblecoating disposed thereon that includes at least one PTH-based agent,(ii) applying the microprojection member to a skin site on the subject,whereby the microprojections pierce the stratum corneum and deliver thePTH-based agent to the subject.

Preferably, the coated microprojection member is applied to the skinsite via an impact applicator.

Also preferably, the coated microprojection member is preferably left onthe skin site for a period lasting from 5 seconds to 24 hours. Followingthe desired wearing time, the microprojection member is removed. In someembodiments, wherein the PTH-based agent is in the range ofapproximately 1 μg-1000 μg of the biocompatible coating.

Further, the pharmacokinetic profile of the transdermally deliveredPTH-based agent is preferably at least similar to the pharmacokineticprofile observed following subcutaneous delivery.

In one preferred embodiment, the PTH-based agent is selected from thegroup consisting of hPTH (1-34), hPTH salts and analogs, teriparatideand related peptides. Also preferably, the hPTH salt is selected fromgroup consisting of acetate, propionate, butyrate, pentanoate,hexanoate, heptanoate, levulinate, chloride, bromide, citrate,succinate, maleate, glycolate, gluconate, glucuronate,3-hydroxyisobutyrate, tricarballylicate, malonate, adipate, citraconate,glutarate, itaconate, mesaconate, citramalate, dimethylolpropinate,tiglicate, glycerate, methacrylate, isocrotonate, β-hydroxibutyrate,crotonate, angelate, hydracrylate, ascorbate, aspartate, glutamate,2-hydroxyisobutyrate, lactate, malate, pyruvate, fumarate, tartarate,nitrate, phosphate, benzene, sulfonate, methane sulfonate, sulfate andsulfonate

In the methods of the invention, transdermal delivery of a PTH-basedagent preferably exhibits rapid on-set of biological action. Alsopreferably, transdermal delivery of a PTH-based agent exhibits sustainedbiological action for a period of up to 8 hours.

In one embodiment, the transdermally delivered PTH-based agent comprisesteriparatide (hPTH (1-34)) and the biocompatible coating comprises adose of the PTH-based agent in the range of approximately 10-100 μgdose, wherein delivery of the PTH-based agent results in a plasmaC_(max) of at least 50 pg/mL after one application.

The invention also comprises a method of improving the pharmacokineticsof a transdermally delivered PTH-based agent comprising providing amicroprojection member having a plurality of stratum corneum-piercingmicroprojections, the microprojection member having a biocompatiblecoating disposed thereon that includes at least one PTH-based agent andapplying the microprojection member to a skin site on the subject,whereby the microprojections pierce the stratum corneum and deliver thePTH-based agent to the subject so that delivery of the PTH-based agenthas improved pharmacokinetics compared to the pharmacokineticscharacteristic of subcutaneous delivery.

In the noted embodiments, the improved pharmacokinetics can compriseincreased bioavailability of the PTH-based agent. The improvedpharmacokinetics can also comprise increased in C_(max). Further, theimproved pharmacokinetics can comprise decreased T_(max). The improvedpharmacokinetics can further comprise an enhanced absorption rate of thePTH-based agent.

The apparatus and method of the invention can thus be employed safelyand effectively in the treatment of osteoporosis and bone fractures.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become apparent from the followingand more particular description of the preferred embodiments of theinvention, as illustrated in the accompanying drawings, and in whichlike referenced characters generally refer to the same parts or elementsthroughout the views, and in which:

FIG. 1 is a schematic illustration of a pulsatile concentration profile,according to the invention;

FIG. 2 is a perspective view of a portion of one example of amicroprojection member, according to the invention;

FIG. 3 is a perspective view of the microprojection member shown in FIG.2 having a coating deposited on the microprojections, according to theinvention;

FIG. 4 is a side sectional view of a microprojection member having anadhesive backing, according to the invention;

FIG. 5 is a side sectional view of a retainer having a microprojectionmember disposed therein, according to the invention;

FIG. 6 is a perspective view of the retainer shown in FIG. 4;

FIG. 7 is an exploded perspective view of an applicator and retainer,according to the invention;

FIG. 8 is a graph illustrating the charge profile for a PTH-based agent,according to the invention;

FIG. 9 is a graph illustrating the mole ratios of a net-charged speciesof a PTH-based agent, according to the invention;

FIG. 10 is a graph illustrating the mole ratios of acetic acid and theneutral form of a PTH-based agent, according to the invention;

FIG. 11 is a graph comparing plasma concentration of a PTH-based agentfollowing transdermal and subcutaneous delivery, according to theinvention;

FIG. 12 is a graph illustrating the aggregation percentage of aPTH-based agent with and without sucrose as a stabilizer, according tothe invention;

FIG. 13 is a graph illustrating the oxidation of a PTH-based agent withand without antioxidants over time, according to the invention;

FIG. 14 is a graph illustrating the plasma concentration of a PTH-basedagent following transdermal delivery, according to the invention;

FIG. 15 is a graph illustrating urinary concentrations of cAMP thatreflects the bioavailability of a PTH-based agent, according to theinvention; and

FIG. 16 is a further graph comparing plasma concentration of a PTH-basedagent following transdermal and subcutaneous delivery, according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the present invention in detail, it is to beunderstood that this invention is not limited to particularlyexemplified materials, methods or structures as such may, of course,vary. Thus, although a number of materials and methods similar orequivalent to those described herein can be used in the practice of thepresent invention, the preferred materials and methods are describedherein.

It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments of the invention only andis not intended to be limiting.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one having ordinaryskill in the art to which the invention pertains.

Further, all publications, patents and patent applications cited herein,whether supra or infra, are hereby incorporated by reference in theirentirety.

Finally, as used in this specification and the appended claims, thesingular forms “a, “an” and “the” include plural referents unless thecontent clearly dictates otherwise. Thus, for example, reference to “anactive agent” includes two or more such agents; reference to “amicroprojection” includes two or more such microprojections and thelike.

DEFINITIONS

The term “transdermal”, as used herein, means the delivery of an agentinto and/or through the skin for local or systemic therapy.

The term “transdermal flux”, as used herein, means the rate oftransdermal delivery.

The terms “pulsatile delivery profile” and “pulsatile concentrationprofile”, as used herein, mean a post administration increase in bloodserum concentration of a PTH-based agent from a baseline concentrationto a concentration in the range of approximately 50-1000 pg/mL in aperiod ranging from 1 min. to 4 hr., wherein C_(max) is achieved, and adecrease in blood serum concentration from C_(max) to the baselineconcentration in a period ranging from 1-8 hrs. after C_(max) has beenachieved. As illustrated in FIG. 1, the noted concentration (orpharmacokinetic) profile typically reflects a rapid rise in blood serumconcentration after administration (i.e., first region) and a slightlyless rapid decline (i.e., second region) relative to the first regionafter C_(max) has been reached, which is generally reflected by a spikein the concentration profile.

Other concentration profiles resulting in a pulsatile deliverycomprising a rise in blood concentration of the PTH-based agent to aC_(max) of 50-1000 pg/mL within a twelve-hour period followingadministration would also likely result in the desired beneficial effectand, hence, are within the scope of the present invention.

As discussed in detail herein, in one embodiment of the invention, thenoted “pulsatile delivery profile” is reflected (or evidenced) by acurve of PTH-based agent concentration in the host's blood serum versustime having an area under the curve (AUC) in the range of approximately0.014-5.24 h·ng/mL and a C_(max) in the range of approximately 0.13-0.72ng/mL for a microprojection member nominally containing 30 μg PTH(1-34).

The term “co-delivering”, as used herein, means that a supplementalagent(s) is administered transdermally either before the PTH-based agentis delivered, before and during transdermal flux of the PTH-based agent,during transdermal flux of the PTH-based agent, during and aftertransdermal flux of the PTH-based agent, and/or after transdermal fluxof the PTH-based agent. Additionally, two or more PTH-based agents maybe formulated in the coatings and/or formulations, resulting inco-delivery of the PTH-based agents.

The terms “PTH-based agent” and “hPTH (1-34) agent”, as used herein,include, without limitation, hPTH (1-34), hPTH salts, hPTH analogs,teriparatide, closely related peptides and agents having a peptidesequence that functions by the same means as the 34 N-terminal aminoacids (the biologically active region) sequence of the 84-amino acidhuman parathyroid hormone. The terms “PTH-based agent” and “hPTH (1-34)agent” thus include, without limitation, recombinant hPTH (1-34),synthetic hPTH (1-34), PTH (1-34), hPTH (1-34) salts, teriparatide,simple derivatives of hPTH (1-34), such as hPTH (1-34) amide and closelyrelated molecules, such as hPTH (1-33) or hPTH (1-31) amide and closelyrelated osteogenic peptides.

Examples of suitable hPTH salts include, without limitation, acetate,propionate, butyrate, pentanoate, hexanoate, heptanoate, levulinate,chloride, bromide, citrate, succinate, maleate, glycolate, gluconate,glucuronate, 3-hydroxyisobutyrate, tricarballylicate, malonate, adipate,citraconate, glutarate, itaconate, mesaconate, citramalate,dimethylolpropinate, tiglicate, glycerate, methacrylate, isocrotonate,β-hydroxibutyrate, crotonate, angelate, hydracrylate, ascorbate,aspartate, glutamate, 2-hydroxyisobutyrate, lactate, malate, pyruvate,fumarate, tartarate, nitrate, phosphate, benzene, sulfonate, methanesulfonate, sulfate and sulfonate.

The noted PTH-based agents can also be in various forms, such as freebases, acids, charged or uncharged molecules, components of molecularcomplexes or nonirritating, pharmacologically acceptable salts.

It is to be understood that more than one PTH-based agent can beincorporated into the agent source, reservoirs, and/or coatings of thisinvention, and that the use of the term “PTH-based agent” in no wayexcludes the use of two or more such agents.

The term “microprojections”, as used herein, refers to piercing elementswhich are adapted to pierce or cut through the stratum corneum into theunderlying epidermis layer, or epidermis and dermis layers, of the skinof a living animal, particularly a mammal and more particularly a human.

In one embodiment of the invention, the piercing elements have aprojection length less than 1000 microns. In a further embodiment, thepiercing elements have a projection length of less than 500 microns,more preferably, less than 250 microns. The microprojections furtherhave a width (designated “W” in FIG. 1) in the range of approximately25-500 microns and a thickness in the range of approximately 10-100microns. The microprojections may be formed in different shapes, such asneedles, blades, pins, punches, and combinations thereof.

The term “microprojection member”, as used herein, generally connotes amicroprojection array comprising a plurality of microprojectionsarranged in an array for piercing the stratum corneum. Themicroprojection member can be formed by etching or punching a pluralityof microprojections from a thin sheet and folding or bending themicroprojections out of the plane of the sheet to form a configuration,such as that shown in FIG. 2. The microprojection member can also beformed in other known manners, such as by forming one or more stripshaving microprojections along an edge of each of the strip(s) asdisclosed in U.S. Pat. No. 6,050,988, which is hereby incorporated byreference in its entirety.

The term “coating formulation”, as used herein, is meant to mean andinclude a freely flowing composition or mixture that is employed to coatthe microprojections and/or arrays thereof. Preferably, the coatingformulation includes at least one PTH-based agent, which can be insolution or suspension in the formulation.

The term “biocompatible coating” and “solid coating”, as used herein, ismeant to mean and include a “coating formulation” in a substantiallysolid state.

As indicated above, the present invention generally comprises a deliverysystem including microprojection member (or system) having a pluralityof microprojections (or array thereof) that are adapted to piercethrough the stratum corneum into the underlying epidermis layer, orepidermis and dermis layers.

As discussed in detail herein, a key advantage of the present inventionis that the delivery system delivers the PTH-based agent to a mammalianhost, particularly, a human patient, whereby the PTH-based agent in thepatient's serum after administration exhibits a preferred pulsatileconcentration profile. The delivery system is further amenable toself-administration of a 20 μg bolus dose of a PTH-based agent at leastonce daily.

Referring now to FIG. 2, there is shown one embodiment of amicroprojection member 30 for use with the present invention. Asillustrated in FIG. 2, the microprojection member 30 includes amicroprojection array 32 having a plurality of microprojections 34. Themicroprojections 34 preferably extend at substantially a 90° angle fromthe sheet, which in the noted embodiment includes openings 38.

According to the invention, the sheet 36 can be incorporated into adelivery patch, including a backing 40 for the sheet 36, and canadditionally include adhesive 16 for adhering the patch to the skin (seeFIG. 4). In this embodiment, the microprojections 34 are formed byetching or punching a plurality of microprojections 34 from a thin metalsheet 36 and bending the microprojections 34 out of the plane of thesheet 36.

In one embodiment of the invention, the microprojection member 30 has amicroprojection density of at least approximately 10microprojections/cm², more preferably, in the range of at leastapproximately 200-2000 microprojections/cm². Preferably, the number ofopenings per unit area through which the agent passes is at leastapproximately 10 openings/cm² and less than about 2000 openings/cm².

As indicated, the microprojections 34 preferably have a projectionlength less than 1000 microns. In one embodiment, the microprojections34 have a projection length of less than 500 microns, more preferably,less than 250 microns. The microprojections 34 also preferably have awidth in the range of approximately 25-500 microns and thickness in therange of approximately 10-100 microns.

In further embodiments of the invention, the biocompatibility of themicroprojection member 30 can be improved to minimize or eliminatebleeding and irritation following application to the skin of a subject.Specifically, the microprojections 34 can have a length less than 145microns, more preferably, in the range of approximately 50-145 microns,and even more preferably, in the range of approximately 70-140 microns.Also, the microprojection member 30 comprises an array preferably havinga microprojection density greater than 100 microprojections/cm², andmore preferably, in the range of approximately 200-3000microprojections/cm². Further details regarding microprojection membershaving improved biocompatibility are found in U.S. Application Ser. No.60/______, Feb. 15, 2005 [ALZ5174 PSP], which is hereby incorporated byreference in its entirety.

The microprojection member 30 can be manufactured from various metals,such as stainless steel, titanium, nickel titanium alloys, or similarbiocompatible materials.

According to the invention, the microprojection member 30 can also beconstructed out of a non-conductive material, such as a polymericmaterial. Alternatively, the microprojection member can be coated with anon-conductive material, such as Parylene®, or a hydrophobic material,such as Teflon®, silicon or other low energy material. The notedhydrophobic materials and associated base (e.g., photoreist) layers areset forth in U.S. Application No. 60/484,142, which is incorporated byreference herein in its entirety.

Microprojection members that can be employed with the present inventioninclude, but are not limited to, the members disclosed in U.S. Pat. Nos.6,083,196, 6,050,988 and 6,091,975, which are incorporated by referenceherein in their entirety.

Other microprojection members that can be employed with the presentinvention include members formed by etching silicon using silicon chipetching techniques or by molding plastic using etched micro-molds, suchas the members disclosed U.S. Pat. No. 5,879,326, which is incorporatedby reference herein in its entirety.

In certain embodiments of the invention, the microprojections 34 arepreferably configured to reduce variability in the applied coating 35.Suitable microprojections generally comprise a location having a maximumwidth transverse to the longitudinal axis that is located at a positionin the range of approximately 25% to 75% of the length of themicroprojection from the distal tip. Proximal to the location of maximumwidth, the width of the microprojection tapers to a minimum width.Further details regarding the noted microprojection configurations arefound in U.S. Application Ser. No. 60/649,888, filed Jan. 31, 2005,which is incorporated by reference herein in its entirety.

Referring now to FIG. 3, there is shown a microprojection member 30having microprojections 34 that include a biocompatible coating 35 thatincludes a PTH-based agent. According to the invention, the coating 35can partially or completely cover each microprojection 34. For example,the coating 35 can be in a dry pattern coating on the microprojections34. The coating 35 can also be applied before or after themicroprojections 34 are formed.

According to the invention, the coating 35 can be applied to themicroprojections 34 by a variety of known methods. Preferably, thecoating is only applied to those portions the microprojection member 30or microprojections 34 that pierce the skin (e.g., tips 39).

One such coating method comprises dip-coating. Dip-coating can bedescribed as a means to coat the microprojections by partially ortotally immersing the microprojections 34 into a coating solution. Byuse of a partial immersion technique, it is possible to limit thecoating 35 to only the tips 39 of the microprojections 34.

A further coating method comprises roller coating, which employs aroller coating mechanism that similarly limits the coating 35 to thetips 39 of the microprojections 34. The roller coating method isdisclosed in U.S. application Ser. No. 10/099,604 (Pub. No.2002/0132054), which is incorporated by reference herein in itsentirety. As discussed in detail in the noted application, the disclosedroller coating method provides a smooth coating that is not easilydislodged from the microprojections 34 during skin piercing.

According to the invention, the microprojections 34 can further includemeans adapted to receive and/or enhance the volume of the coating 35,such as apertures (not shown), grooves (not shown), surfaceirregularities (not shown) or similar modifications, wherein the meansprovides increased surface area upon which a greater amount of coatingcan be deposited.

A further coating method that can be employed within the scope of thepresent invention comprises spray coating. According to the invention,spray coating can encompass formation of an aerosol suspension of thecoating composition. In one embodiment, an aerosol suspension having adroplet size of about 10 to 200 picoliters is sprayed onto themicroprojections 10 and then dried.

Pattern coating can also be employed to coat the microprojections 34.The pattern coating can be applied using a dispensing system forpositioning the deposited liquid onto the microprojection surface. Thequantity of the deposited liquid is preferably in the range of 0.1 to 20nanoliters/microprojection. Examples of suitable precision-meteredliquid dispensers are disclosed in U.S. Pat. Nos. 5,916,524; 5,743,960;5,741,554; and 5,738,728; which are fully incorporated by referenceherein.

Microprojection coating formulations or solutions can also be appliedusing ink jet technology using known solenoid valve dispensers, optionalfluid motive means and positioning means which is generally controlledby use of an electric field. Other liquid dispensing technology from theprinting industry or similar liquid dispensing technology known in theart can be used for applying the pattern coating of this invention.

Referring now to FIGS. 5 and 6, for storage and application, themicroprojection member 30 is preferably suspended in a retainer ring 40by adhesive tabs 6, as described in detail in U.S. application Ser. No.09/976,762 (Pub. No. 2002/0091357), which is incorporated by referenceherein in its entirety.

After placement of the microprojection member 30 in the retainer ring40, the microprojection member 30 is applied to the patient's skin.Preferably, the microprojection member 30 is applied to the patient'sskin using an impact applicator 45, such as shown in FIG. 7 anddescribed in Co-Pending U.S. application Ser. No. 09/976,978, which isincorporated by reference herein in its entirety.

As indicated, according to one embodiment of the invention, the coatingformulations applied to the microprojection member 30 to form solidbiocompatible coatings can comprise aqueous and non-aqueous formulationshaving at least one PTH-based agent. According to the invention, thePTH-based agent can be dissolved within a biocompatible carrier orsuspended within the carrier.

Referring now to FIG. 8, there is shown the predicted charge profile ofhPTH (1-34), a peptide exhibiting 11 acidic pKa's and 6 basic pKa's. Asillustrated in FIG. 8, the peptide presents a zero net electric chargeat pH 9. This point is also called the isoelectric point or pI.

Referring now to FIG. 9, there is shown the predicted mole ratios of thenet charged species of hPTH (1-34). As illustrated in FIG. 8, theneutral species only exist in significant amounts in the pH range of pH6.5 to pH 11.5. In this pH range, the peptide has reduced watersolubility and may precipitate out of solution. hPTH and closely relatedanalogs thereof exhibit similar characteristics and behave similarly tohPTH (1-34).

The data thus reflects that hPTH (1-34) solubility that is compatiblewith formulations acceptable for coating on a microprojection array ofthe invention can be achieved at a pH below about pH 6 or above pH 11.5.Accordingly, in a preferred embodiment, the pH of the coatingformulation is in the range of approximately pH 2-pH 6.

Referring now to FIG. 10, there is shown a superposition of the moleratios for acetic acid and the neutral form of hPTH (1-34). Asillustrated in FIG. 8, the pH of a PTH hexaacetate (mole ratio 1 to 6)in solution is about pH 5. At pH 5, negligible amounts of PTH arepresent as PTH zero net charge (PTH 0). The PTH is also highly solublein water at concentrations in excess of 20%. During drying andsubsequent storage, the free acetic acid will evaporate inherentlyresulting in formation of the water insoluble PTH 0. Subsequentreconstitution in water will not allow total solubilization of PTH.Accordingly, the use of a low volatility counterion provides a solidsoluble formulation of PTH as long as the pH is maintained at least 2.5pH units, preferably 3 pH units, below the pI of PTH. Preferably, thiscan be achieved by providing at least about two low volatilitycounterions to each molecule of PTH.

Therefore, in one embodiment of the invention, the coating formulationsinclude a counterion or a mixture of counterions. Further, in thepreferred pH range of pH 3-pH 6, the PTH-based agent will bear apositive charge.

In a preferred embodiment, the PTH-based agent is selected from thegroup consisting of hPTH (1-34), hPTH salts and analogs, teriparatideand related peptides, including, recombinant hPTH (1-34), synthetic hPTH(1-34), PTH (1-34), teriparatide, hPTH (1-34) salts, simple derivativesof hPTH (1-34), such as hPTH (1-34) amide, and closely relatedmolecules, such as hPTH (1-33) or hPTH (1-31) amide, and any otherclosely related osteogenic peptide. Synthetic hPTH (1-34) is the mostpreferred PTH-based agent.

Examples of suitable hPTH salts include, without limitation, acetate,propionate, butyrate, pentanoate, hexanoate, heptanoate, levulinate,chloride, bromide, citrate, succinate, maleate, glycolate, gluconate,glucuronate, 3-hydroxyisobutyrate, tricarballylicate, malonate, adipate,citraconate, glutarate, itaconate, mesaconate, citramalate,dimethylolpropinate, tiglicate, glycerate, methacrylate, isocrotonate,β-hydroxibutyrate, crotonate, angelate, hydracrylate, ascorbate,aspartate, glutamate, 2-hydroxyisobutyrate, lactate, malate, pyruvate,fumarate, tartarate, nitrate, phosphate, benzene, sulfonate, methanesulfonate, sulfate and sulfonate.

Preferably, the PTH-based agent is present in the coating formulation ata concentration in the range of approximately 1-30 wt. %.

More preferably, the amount of PTH-based agent contained in thebiocompatible coating on the microprojection member is in the range of1-1000 μg, even more preferably, in the range of 10-100 μg.

Preferably, the pH of the coating formulation is below about pH 6. Morepreferably, the coating formulation has a pH in the range of pH 2-pH 6.Even more preferably, the coating formulation has a pH in the range ofapproximately pH 3-pH 6.

In certain embodiments of the invention, the viscosity of the coatingformulation is enhanced by adding low volatility counterions. In oneembodiment, the PTH-based agent has a positive charge at the formulationpH and the viscosity-enhancing counterion comprises an acid having atleast two acidic pKas. Suitable acids include, without limitation,maleic acid, malic acid, malonic acid, tartaric acid, adipic acid,citraconic acid, fumaric acid, glutaric acid, itaconic acid, meglutol,mesaconic acid, succinic acid, citramalic acid, tartronic acid, citricacid, tricarballylic acid, ethylenediaminetetraacetic acid, asparticacid, glutamic acid, carbonic acid, sulfuric acid and phosphoric acid.

Another preferred embodiment is directed to a viscosity-enhancingmixture of counterions, wherein the PTH-based agent has a positivecharge at the formulation pH and at least one of the counterionscomprises an acid having at least two acidic pKas. The other counterionis an acid with one or more pKas. Examples of suitable acids include,without limitation, hydrochloric acid, hydrobromic acid, nitric acid,sulfuric acid, maleic acid, phosphoric acid, benzene sulfonic acid,methane sulfonic acid, citric acid, succinic acid, glycolic acid,gluconic acid, glucuronic acid, lactic acid, malic acid, pyruvic acid,tartaric acid, tartronic acid, fumaric acid, acetic acid, propionicacid, pentanoic acid, carbonic acid, malonic acid, adipic acid,citraconic acid, levulinic acid, glutaric acid, itaconic acid, meglutol,mesaconic acid, citramalic acid, citric acid, aspartic acid, glutamicacid, tricarballylic acid and ethylenediaminetetraacetic acid.

In the noted embodiments of the invention, the amount of counterion ispreferably sufficient to neutralize the charge of the PTH. In suchembodiments, the counterion or the mixture of counterion is preferablysufficient to neutralize the charge present on the agent at the pH ofthe formulation. In additional embodiments, excess counterion (as thefree acid or as a salt) is added to the peptide to control pH andprovide adequate buffering capacity.

In one preferred embodiment, the agent comprises hPTH (1-34) and thecounterion comprises a viscosity-enhancing mixture of counterions chosenfrom the group consisting of citric acid, tartaric acid, malic acid,hydrochloric acid, glycolic acid and acetic acid. Preferably, thecounterions are added to the formulation to achieve a viscosity in therange of about 20-200 cp.

In a preferred embodiment, the viscosity-enhancing counterion comprisesan acidic counterion, such as a low volatility weak acid. Preferably,the low volatility weak acid counterion exhibits at least one acidic pKaand a melting point higher than about 50° C. or a boiling point higherthan about 170° C. at P_(atm). Examples of such acids include, withoutlimitation, citric acid, succinic acid, glycolic acid, gluconic acid,glucuronic acid, lactic acid, malic acid, pyruvic acid, tartaric acid,tartronic acid and fumaric acid.

In another embodiment, the counterion comprises a strong acid.Preferably, the strong acid exhibits at least one pKa lower than about2. Examples of such acids include, without limitation, hydrochloricacid, hydrobromic acid, nitric acid, sulfonic acid, sulfuric acid,maleic acid, phosphoric acid, benzene sulfonic acid and methane sulfonicacid.

Another preferred embodiment is directed to a mixture of counterions,wherein at least one of the counterion comprises a strong acid and atleast one of the counterions comprises a low volatility weak acid.

Another preferred embodiment is directed to a mixture of counterions,wherein at least one of the counterions comprises a strong acid and atleast one of the counterions comprises a weak acid with high volatility.Preferably, the volatile weak acid counterion exhibits at least one pKahigher than about 2 and a melting point lower than about 50° C. or aboiling point lower than about 170° C. at P_(atm). Examples of suchacids include, without limitation, acetic acid, propionic acid,pentanoic acid and the like.

The acidic counterion is preferably present in an amount sufficient toneutralize the positive charge present on the PTH-based agent at the pHof the formulation. In additional embodiments, excess counterion (as thefree acid or as a salt) is added to control pH and to provide adequatebuffering capacity.

In another embodiment of the invention, the coating formulation includesat least one buffer. Examples of such buffers include, withoutlimitation, ascorbic acid, citric acid, succinic acid, glycolic acid,gluconic acid, glucuronic acid, lactic acid, malic acid, pyruvic acid,tartaric acid, tartronic acid, fumaric acid, maleic acid, phosphoricacid, tricarballylic acid, malonic acid, adipic acid, citraconic acid,glutaratic acid, itaconic acid, mesaconic acid, citramalic acid,dimethylolpropionic acid, tiglic acid, glyceric acid, methacrylic acid,isocrotonic acid, β-hydroxybutyric acid, crotonic acid, angelic acid,hydracrylic acid, aspartic acid, glutamic acid, glycine and mixturesthereof.

In one embodiment of the invention, the coating formulation includes atleast one antioxidant, which can be sequestering agents, such sodiumcitrate, citric acid, EDTA (ethylene-dinitrilo-tetraacetic acid) or freeradical scavengers such as ascorbic acid, methionine, sodium ascorbateand the like. Presently preferred antioxidants comprise EDTA andmethionine.

In the noted embodiments of the invention, the concentration of theantioxidant is in the range of approximately 0.01-20 wt. % of thecoating formulation. Preferably the antioxidant is in the range ofapproximately 0.03-10 wt. % of the coating formulation.

In one embodiment of the invention, the coating formulation includes atleast one surfactant, which can be zwitterionic, amphoteric, cationic,anionic, or nonionic, including, without limitation, sodiumlauroamphoacetate, sodium dodecyl sulfate (SDS), cetylpyridiniumchloride (CPC), dodecyltrimethyl ammonium chloride (TMAC), benzalkonium,chloride, polysorbates, such as Tween 20 and Tween 80, other sorbitanderivatives, such as sorbitan laurate, alkoxylated alcohols, such aslaureth-4 and polyoxyethylene castor oil derivatives, such as CremophorEL®.

In one embodiment of the invention, the concentration of the surfactantis in the range of approximately 0.01-20 wt. % of the coatingformulation. Preferably the surfactant is in the range of approximately0.05-1 wt. % of the coating formulation.

In a further embodiment of the invention, the coating formulationincludes at least one polymeric material or polymer that has amphiphilicproperties, which can comprise, without limitation, cellulosederivatives, such as hydroxyethylcellulose (HEC),hydroxypropylmethylcellulose (HPMC), hydroxypropycellulose (HPC),methylcellulose (MC), hydroxyethylmethylcellulose (HEMC), orethylhydroxy-ethylcellulose (EHEC), as well as pluronics.

In one embodiment of the invention, the concentration of the polymerpresenting amphiphilic properties in the coating formulation ispreferably in the range of approximately 0.01-20 wt. %, more preferably,in the range of approximately 0.03-10 wt. % of the coating formulation.

In another embodiment, the coating formulation includes a hydrophilicpolymer selected from the following group: hydroxyethyl starch,carboxymethyl cellulose and salts of, dextran, poly(vinyl alcohol),poly(ethylene oxide), poly(2-hydroxyethylmethacrylate), poly(n-vinylpyrolidone), polyethylene glycol and mixtures thereof, and likepolymers.

In a preferred embodiment, the concentration of the hydrophilic polymerin the coating formulation is in the range of approximately 1-30 wt. %,more preferably, in the range of approximately 1-20 wt. % of the coatingformulation.

In another embodiment of the invention, the coating formulation includesa biocompatible carrier, which can comprise, without limitation, humanalbumin, bioengineered human albumin, polyglutamic acid, polyasparticacid, polyhistidine, pentosan polysulfate, polyamino acids, sucrose,trehalose, melezitose, raffinose, stachyose, mannitol, and other sugaralcohols.

Preferably, the concentration of the biocompatible carrier in thecoating formulation is in the range of approximately 2-70 wt. %, morepreferably, in the range of approximately 5-50 wt. % of the coatingformulation.

In another embodiment, the coating formulation includes a stabilizingagent, which can comprise, without limitation, a non-reducing sugar, apolysaccharide or a reducing sugar.

Suitable non-reducing sugars for use in the methods and compositions ofthe invention include, for example, sucrose, trehalose, stachyose, orraffinose.

Suitable polysaccharides for use in the methods and compositions of theinvention include, for example, dextran, soluble starch, dextrin, andinsulin.

Suitable reducing sugars for use in the methods and compositions of theinvention include, for example, monosaccharides such as, for example,apiose, arabinose, lyxose, ribose, xylose, digitoxose, fucose,quercitol, quinovose, rhamnose, allose, altrose, fructose, galactose,glucose, gulose, hamamelose, idose, mannose, tagatose, and the like; anddisaccharides such as, for example, primeverose, vicianose, rutinose,scillabiose, cellobiose, gentiobiose, lactose; lactulose, maltose,melibiose, sophorose, and turanose, and the like.

Preferably, the concentration of the stabilizing agent in the coatingformulation is at ratio of approximately 0.1-2.0:1 with respect to thePTH-based agent, more preferably, approximately 0.25-1.0:1 with respectto the PTH-based agent.

In another embodiment, the coating formulation includes avasoconstrictor, which can comprise, without limitation, amidephrine,cafaminol, cyclopentamine, deoxyepinephrine, epinephrine, felypressin,indanazoline, metizoline, midodrine, naphazoline, nordefrin, octodrine,ornipressin, oxymethazoline, phenylephrine, phenylethanolamine,phenylpropanolamine, propylhexedrine, pseudoephedrine, tetrahydrozoline,tramazoline, tuaminoheptane, tymazoline, vasopressin, xylometazoline andthe mixtures thereof. The most preferred vasoconstrictors includeepinephrine, naphazoline, tetrahydrozoline indanazoline, metizoline,tramazoline, tymazoline, oxymetazoline and xylometazoline.

As will be appreciated by one having ordinary skill in the art, theaddition of a vasoconstrictor to the coating formulations and, hence,solid biocompatible coatings of the invention is particularly useful toprevent bleeding that can occur following application of themicroprojection member or array and to prolong the pharmacokinetics ofthe PTH-based agent through reduction of the blood flow at theapplication site and reduction of the absorption rate from the skin siteinto the system circulation.

The concentration of the vasoconstrictor, if employed, is preferably inthe range of approximately 0.1 wt. % to 10 wt. % of the coatingformulation.

In another embodiment of the invention, the coating formulation includesat least one “pathway patency modulator”, which can comprise, withoutlimitation, osmotic agents (e.g., sodium chloride), zwitterioniccompounds (e.g., amino acids), and anti-inflammatory agents, such asbetamethasone 21-phosphate disodium salt, triamcinolone acetonide21-disodium phosphate, hydrocortamate hydrochloride, hydrocortisone21-phosphate disodium salt, methylprednisolone 21-phosphate disodiumsalt, methylprednisolone 21-succinate sodium salt, paramethasonedisodium phosphate and prednisolone 21-succinate sodium salt, andanticoagulants, such as citric acid, citrate salts (e.g., sodiumcitrate), dextrin sulfate sodium, aspirin and EDTA.

In yet another embodiment of the invention, the coating formulationincludes a solubilising/complexing agent, which can compriseAlpha-Cyclodextrin, Beta-Cyclodextrin, Gamma-Cyclodextrin,glucosyl-alpha-Cyclodextrin, maltosyl-alpha-Cyclodextrin,glucosyl-beta-Cyclodextrin, maltosyl-beta-Cyclodextrin, hydroxypropylbeta-Cyclodextrin, 2-hydroxypropyl-beta-Cyclodextrin,2-hydroxypropyl-gamma-Cyclodextrin, hydroxyethyl-beta-Cyclodextrin,methyl-beta-Cyclodextrin, sulfobutylether-alpha-Cyclodextrin,sulfobutylether-beta-Cyclodextrin, andsulfobutylether-gamma-Cyclodextrin. Most preferredsolubilising/complexing agents are beta-Cyclodextrin, hydroxypropylbeta-Cyclodextrin, 2-hydroxypropyl-beta-Cyclodextrin andsulfobutylether7 beta-Cyclodextrin.

The concentration of the solubilising/complexing agent, if employed, ispreferably in the range of approximately 1 wt. % to 20 wt. % of thecoating formulation.

In another embodiment of the invention, the coating formulation includesat least one non-aqueous solvent, such as ethanol, isopropanol,methanol, propanol, butanol, propylene glycol, dimethysulfoxide,glycerin, N,N-dimethylformamide and polyethylene glycol 400. Preferably,the non-aqueous solvent is present in the coating formulation in therange of approximately 1 wt. % to 50 wt. % of the coating formulation.

Other known formulation adjuvants can also be added to the coatingformulations provided they do not adversely affect the necessarysolubility and viscosity characteristics of the coating formulation andthe physical integrity of the dried coating.

Preferably, the coating formulations have a viscosity less thanapproximately 500 centipoise and greater than 3 centipoise.

In one embodiment of the invention, the thickness of the biocompatiblecoating is less than 25 microns, more preferably, less than 10 microns,as measured from the microprojection surface.

The desired coating thickness is dependent upon several factors,including the required dosage and, hence, coating thickness necessary todeliver the dosage, the density of the microprojections per unit area ofthe sheet, the viscosity and concentration of the coating compositionand the coating method chosen.

In accordance with one embodiment of the invention, the method fordelivering a PTH-based agent contained in the biocompatible coating onthe microprojection member includes the following steps: the coatedmicroprojection member is initially applied to the patient's skin via anactuator, wherein the microprojections pierce the stratum corneum. Thecoated microprojection member is preferably left on the skin for aperiod lasting from 5 seconds to 24 hours. Following the desired wearingtime, the microprojection member is removed.

Preferably, the amount of PTH-based agent contained in the biocompatiblecoating (i.e., dose) is in the range of approximately 1 μg-1000 μg, morepreferably, in the range of approximately 10-200 μg per dosage unit.Even more preferably, the amount of PTH-based agent contained in thebiocompatible coating is in the range of approximately 10-100 μg perdosage unit.

As stated, according to the invention, the PTH-based agent is deliveredto the patient in a pulsatile fashion and, hence, exhibitpharmacokinetics resulting in a pulsatile concentration profile. In oneembodiment of the invention, the pulsatile concentration profile isreflected (or evidenced) by a curve of PTH-based agent concentration inthe host's blood serum versus time having an area under the curve (AUC)in the range of approximately 0.014-5.24 h·ng/mL and a C_(max) in therange of approximately 0.13-0.72 ng/mL for a microprojection membernominally containing 30 μg PTH (1-34).

In a further embodiment of the invention, the pulsatile concentrationprofile is reflected (or evidenced) by a curve of PTH-based agentconcentration in the host's blood serum versus time having an area underthe curve (AUC) in the range of approximately 0.014-5.24 h·ng/mL,C_(max) in the range of approximately 0.13-0.72 ng/mL and T_(max) in therange of 5-15 min. for a microprojection member nominally containing 30μg PTH (1-34).

In a presently preferred embodiment, a 20 μg bolus dose of a PTH-basedagent is delivered in a pulsatile fashion by leaving the microprojectionmember in place for 15 minutes or less.

The noted pulsatile concentration profiles are preferably achieved via aPTH delivery regime in the range of 0.5 (i.e., once every other day)—2pulses per day, more preferably, one full pulse (or dose) per day.However, as will be appreciated by one having ordinary skill in the art,the PTH can also be delivered via various additional dosing regimes.

In all cases, after a coating has been applied, the coating formulationis dried onto the microprojections 34 by various means. In a preferredembodiment of the invention, the coated microprojection member 30 isdried in ambient room conditions. However, various temperatures andhumidity levels can be used to dry the coating formulation onto themicroprojections. Additionally, the coated member can be heated,lyophilized, freeze dried or similar techniques used to remove the waterfrom the coating.

It will be appreciated by one having ordinary skill in the art that inorder to facilitate drug transport across the skin barrier, the presentinvention can also be employed in conjunction with a wide variety ofiontophoresis or electrotransport systems, as the invention is notlimited in any way in this regard. Illustrative electrotransport drugdelivery systems are disclosed in U.S. Pat. Nos. 5,147,296, 5,080,646,5,169,382 and 5,169,383, the disclosures of which are incorporated byreference herein in their entirety.

The term “electrotransport” refers, in general, to the passage of abeneficial agent, e.g., a drug or drug precursor, through a body surfacesuch as skin, mucous membranes, nails, and the like. The transport ofthe agent is induced or enhanced by the application of an electricalpotential, which results in the application of electric current, whichdelivers or enhances delivery of the agent, or, for “reverse”electrotransport, samples or enhances sampling of the agent. Theelectrotransport of the agents into or out of the human body may byachieved in various manners.

One widely used electrotransport process, iontophoresis, involves theelectrically induced transport of charged ions. Electroosmosis, anothertype of electrotransport process involved in the transdermal transportof uncharged or neutrally charged molecules (e.g., transdermal samplingof glucose), involves the movement of a solvent with the agent through amembrane under the influence of an electric field. Electroporation,still another type of electrotransport, involves the passage of an agentthrough pores formed by applying an electrical pulse, a high voltagepulse, to a membrane.

In many instances, more than one of the noted processes may be occurringsimultaneously to different extents. Accordingly, the term“electrotransport” is given herein its broadest possible interpretation,to include the electrically induced or enhanced transport of at leastone charged or uncharged agent, or mixtures thereof, regardless of thespecific mechanism(s) by which the agent is actually being transported.Additionally, other transport enhancing methods, such as sonophoresis orpiezoelectric devices, can be used in conjunction with the invention.

EXAMPLES

The following examples are given to enable those skilled in the art tomore clearly understand and practice the present invention. They shouldnot be considered as limiting the scope of the invention, but merely asbeing illustrated as representative thereof.

Example 1

Delivery of hPTH (1-34) from coated microprojection arrays was evaluatedin a hairless guinea pig (HGP) model. Microprojection arrays wereproduced using photo/chemical etching, and forming. The microprojectionarrays used in this study were 2 cm² in area, with 320microprojections/cm² and a projection length of 200 μm.

The microprojection arrays were coated with a 25% aqueous solution ofhPTH (1-34) at 40±10 μg per 2 cm² array, with a solid coating limited tothe first 100 μm of the microprojections. Each coated microprojectionarray was assembled to a flexible polymeric adhesive backing. Theresulting patch was assembled onto a retainer ring and loaded on areusable impact applicator at the time of application to the HGP.

Each anesthetized HGP received a patch that was applied to a clean skinarea for a wearing time of 1 hour. At various time intervals followingpatch application, blood samples were taken. Plasma hPTH (1-34) levelswere determined using an enzyme immunoassay (Peninsula Lab).

The plasma levels of HGPs receiving microprojection array patches coatedwith 40 μg of hPTH (1-34) were compared with subcutaneous (SC)administration of 20 μg of hPTH (1-34) (see FIG. 11).

An intravenous (IV) injection of 23 μg hPTH (1-34) was also performed ina separate group of 5 animals and the area under the curve (AUC) wasused as a reference to calculate the total amounts absorbed/deliveredfollowing SC or microneedle array administration. The pharmacokineticparameters of hPTH (1-34) following IV, SC, and microneedle arrayadministration are shown in Table 1.

The pharmacokinetic (PK) profiles of immunoreactive hPTH (1-34) weresimilar for both SC and microprojection array delivery; t_(max) (SC: 10min vs 20 min, C_(max) (SC: 4.6±1.5 ng/mL vs 3.4±1.0 ng/ml);AUC_(240 min) (SC: 8.2±2.9 μg vs 6.6±1.8 μg) (n=10 per group, mean±SD).

The data indicate that hPTH (1-34) can be transdermally delivered with aPK profile similar to that of subcutaneous injection and highlight thefeasibility of transdermal delivery of hPTH (1-34) using amicroprojection array technology, which could be a more convenientalternative for osteoporotic patients.

TABLE 1 Route of Administration IV SC Array Single Dose Parameters DoseAmount (μg) 22.5 19.5 40.0 Dosage (μg/kg) 30.9 29.2 52.8 Fraction dose100 42 17 absorbed/delivered (%) C_(max) (ng/mL) 71.2 +/− 11.2 4.6 +/−1.5 3.4 +/− 1.0 T_(max) (min) 1 20 10 AUC (ng*h/ml) 13.2 +/− 3.8  5.4+/− 1.7 3.9 +/− 1.1 Dose absorbed/ 8.2 +/− 2.9 6.6 +/− 1.8 delivered(μg)

Example 2

Example 2 demonstrates the utilization of a weak acid with a hPTH (1-34)agent to enhance the viscosity. The interaction of the weak acid anionwith the positively charged a hPTH (1-34) agent leads to the formationof secondary bonds, e.g. hydrogen bonds, which results in an increase insolution viscosity. The greater the number of acidic groups, the greaterthe number of secondary bonds formed between the anions and the hPTH(1-34) agent, hence the greater the viscosity increase. Thus, thetheoretical viscosity enhancing capabilities increase when monoacids,di-acids, tri-acids and tetra-acids are compared.

Various weak acid buffers have been incorporated in the hPTH (1-34)formulations in this experiment. A control formulation including PTH(1-34) acetate with sucrose was also prepared. The experimentinvestigated the physicochemical properties afforded to hPTH (1-34) byvarious mixtures of mono-, di- and tri-acids and the stability of thesolution formulations over a 48 hr period at 2-8° C. The PTH (1-34)formulations were buffered to a pH 5.2.

Referring now to Table 2, there is shown the viscosity results of theformulations. The citric and malic acid buffered formulations exhibitedthe largest increase viscosity enhancement compared to the controlformulation (Lot No. 7528069A). Citric acid, a tri-acid, yielded aformulation with the highest viscosity.

The data reflected in Table 2 demonstrates that counterion mixtures ofcitric acid/acetic acid, malic acid/acetic acid, tartaric acid/aceticacid and hydrochloric acid/acetic acid increase the viscosity of hPTH(1-34) with respect to the control formulation of 20% PTH, 20% Sucrose,0.2% Tween 20. Based on the results reflected in Table 2, the trend forviscosity enhancement following addition of weak acid buffers ispreferably tri-acid to di-acid to mono-acid.

TABLE 2 Formulation Lot No. Viscosity (cP) 20% PTH, 20% Sucrose, 0.2%Tween 20 68 20% PTH, 20% Sucrose, 0.5% HCl, 87 0.2% Tween 20 20% PTH,20% Sucrose, 1.2% glycolic acid, 53 0.2% Tween 20 20% PTH, 20% Sucrose,1.4% malic acid, 116 0.2% Tween 20 20% PTH, 20% Sucrose, 1.2% tartaricacid, 77 0.2% Tween 20 20% PTH, 20% Sucrose, 1.7% citric acid, 172 0.2%Tween 20

Example 3

Example 3 demonstrates the utilization of a mixture of counterions witha hPTH (1-34) agent to enhance the dissolution of hPTH-based agent invivo.

In a solid coating on a microprojection array, the agent is typicallypresent in an amount of less than about 1 mg per unit dose. With theaddition of excipients and counterions, the total mass of solid coatingcan be less than 3 mg per unit dose.

The array is usually present on an adhesive backing, which is attachedto a disposable polymeric retainer ring. This assembly is typicallypackaged individually in a pouch or a polymeric housing. In addition tothe assembly, this package contains an atmosphere (usually inert) thatrepresents a volume of at least 3 mL. This large volume (as compared tothat of the coating) acts as a sink for any volatile component. Forexample, at 20° C., the amount of acetic acid present in a 3 mLatmosphere as a result of its vapor pressure would be about 0.15 mg.This amount is typically what would be present in the solid coating ifacetic acid were used as a counterion. In addition, components of theassembly, such as the adhesive, are likely to act as additional sinksfor volatile components. As a result, during long-term storage, it islikely that the concentration of any volatile component present in thecoating would change dramatically. These conditions are typical ofpackaging of pharmaceutical compounds where large amounts of excipientsare usually present. Even with very potent biotechnology compounds thatare lyophilized for use as an injectable, a very large excess of buffersand excipients is present in the dry cake.

In solution, or in the solid state, volatilization of the counterionoccurs at the interface between the solution or the solid and theatmosphere. High diffusivity of solutes generally minimizes differencesin concentration between the interface and the bulk of the solution.Conversely, in a solid state, diffusivity is very slow and greaterconcentration gradients of the volatile counterion are achieved betweenthe interface and the bulk of the solution. Ultimately, the outer layerof the coating is depleted in counterion while the bulk of the solidcoating is relatively unchanged, as compared to the initial dry state.This situation can result in a highly insoluble outer coating if thecounterion is associated with an agent that is substantially insolublein its neutral net charge state. Indeed, volatilization of thecounterion results in formation of the water insoluble neutral species.This, in turn, jeopardizes dissolution of the agent from the solidcoating upon exposure to the biological fluids. Accordingly, thisexperiment investigated the effect of adding low volatility counterionsto improve coating solubility.

Several aqueous formulations containing hPTH (1-34) were prepared andare set forth in Table 3. These formulations contained the volatilecounterion acetic acid. Certain formulations contained additional lowvolatility counterions hydrochloric acid, glycolic acid, or tartaricacid. The microprojection arrays (microprojection length 200 mm, 595microprojections per array) had a skin contact area of approximately 2cm². The tips of the microprojections were coated with the notedformulations by passing the arrays over a rotating drum carrying the PTHformulations, using the method and apparatus disclosed in U.S. patentapplication Ser. No. 10/099,604, which is hereby incorporated byreference herein.

Four successive coatings were performed on each microprojection array ata temperature of 2-8° C. The amount of peptide coated on the arrays wasevaluated by ultraviolet spectroscopy at a wavelength of 275 nm.Scanning electron microscopy revealed that the solid coating had a verysmooth surface with no evidence of cracking. Furthermore, gooduniformity of coating from microprojection to microprojection wasobserved, with the coating limited to the first 100 μm of themicroprojection tip.

Tip-coated arrays prepared in this manner were subsequently used fordrug delivery studies in hairless guinea pigs (HGPs). HGPs wereanesthetized by intramuscular injection of xylazine (8 mg/kg) andketamine HCl (44 mg/kg). Anesthetized HGPs were catheterized through thecarotid artery. The catheter was flushed with heparinized saline (20IU/mL) to prevent clotting. The HGPs were maintained under anesthesiathroughout the experiment via injection of sodium pentobarbital (32mg/mL) directly into the catheter (0.1 mL/injection). Beforeapplication, blood samples were taken into heparinized vials (finalconcentration of heparin at 15 IU/mL), which served as 0 or baselinesamples.

The application of the coated microprojection arrays was performed onthe flank of the anesthetized animals with a spring-driven impactapplicator (total energy=0.4 Joules, delivered in less than 10milliseconds), of the type disclosed in U.S. patent application Ser. No.09/976,798, which is hereby incorporated in its entirety by referenceherein. The system applied comprised a coated microprojection arraydevice, adhered to the center of a LDPE backing with an adhesive (7 cm2disc). Patches were retained on the skin for 1 h (n=4-5). A controlgroup of animals (n=5) received an intravenous injection of 22 μg hPTH.

Blood samples were collected through the carotid catheter at timeintervals following patch application. All blood samples werecentrifuged immediately for plasma collection, the latter was thenstored at −80° C. until analysis. Plasma hPTH was determined by the EIA,a commercial enzyme immunoassay kit for hPTH from Peninsula Lab. (SanCarlos, Calif.). The hPTH dose delivered by microprojection arrays wasextrapolated based on the area under the curve (AUC) calculationcompared to IV administration of hPTH.

As shown in Table 3, different amounts of PTH were delivered from eachsolid formulation. The solid formulations containing only PTH acetatedelivered less than 2 mg on average. Addition of low volatilitycounterions to PTH acetate increased delivery significantly to up to11.2 mg after the addition of the low volatility counterion glycolicacid. The two other non-counterions tested, i.e., tartaric andhydrochloric acid, also increased PTH delivery. Specifically, thecounterion mixtures of glycolic acid/acetic acid, tartaric acid/aceticacid and hydrochloric acid/acetic acid increased the delivered amount ofhPTH (1-34) with respect to the control formulation of 21.2% PTH, 3.8%acetic acid.

TABLE 3 Ratio (PTH:Acetate:low Amount of PTH Amount volatility coated onarray delivered Formulation solution (wt %) counterion) (μg) ± SD (μg) ±SD 21.2% PTH, 3.8% acetic acid, water (q.s.) 1:3:0 28.0 ± 6.6 1.1 ± 1.121.2% PTH, 3.8% acetic acid, water 1:3:0  35.0 ± 11.4 1.5 ± 1.7 22.3%PTH, 2.7% acetic acid, 1:2:2 40.0 ± 9.8 5.9 ± 2.5 0.4% HCl, water 16.2%PTH, 3.8% acetic acid, 1:3:3 30.5 ± 2.3 6.1 ± 4.0 0.5% HCl, 20.2%excipients, water. 6.2% PTH, 3.8% acetic acid, 2.1% 1:3:4  45.9 ± 11.711.2 ± 2.7  glycolic acid, 12.2% excipients, water. 16.2% PTH, 3.8%acetic acid, 1.2% 1:3:2 29.0 ± 4.3 4.2 ± 1.5 Tartaric acid, 20.23%excipients, water

Example 4

Example 4 demonstrates the utilization of a stabilizing agent with ahPTH (1-34) agent to enhance the stability of the hPTH (1-34) agent.

Ten formulations, as shown in Table 4, were coated on titanium andmonitored for chemical stability at 40° C. for a period of 60 days. ThepH of the formulations containing the weak acid buffers wasapproximately pH 5.2, while the pH of the chloride containingformulations was approximately pH 5.4. The purity, oxidized PTH (1-34)product and soluble aggregates were monitored as a function of time byreverse phase high-pressure liquid chromatography (RPHPLC) and sizeexclusion chromatography (SEC), respectively. The results for eachformulation are summarized in Tables 5-14.

The stability data generated suggests that the main mechanism ofdegradation of PTH in the solid state is via an aggregation process.Furthermore, the stability data indicates that addition of sucroseprevents aggregation of hPTH (1-34). FIG. 12 shows the percentaggregation of hPTH (1-34) formulations with and without sucrose at the60-day time point.

TABLE 4 Formulation Formulation Composition (% w/w) A 20% PTH, 12.7% HClB 20% PTH, 12.7% HCl, 0.01% EDTA C 20% PTH, 12.7% HCl, 1% methionine,0.01% EDTA D 20% PTH, 12.7% HCl, 1.2% Tartaric acid, 1% methionine, 0.2%Tween 20, 0.01% EDTA E 20% PTH, 20% sucrose, 12.7% HCl, 0.2% Tween 20 F20% PTH, 20% sucrose, 12.7% HCl, 0.2% Tween 20, 0.03% EDTA G 20% PTH,20% sucrose, 12.7% HCl, 2% methionine, 0.2% Tween 20, 0.03% EDTA H 20%PTH, 20% sucrose, 1.2% Tartaric acid, 2% methionine, 0.2% Tween 20,0.03% EDTA I 20% PTH, 20% sucrose, 1.2% Glycolic acid, 2% methionine,0.2% Tween 20, 0.03% EDTA J 20% PTH, 20% sucrose, 1.7% Citric acid, 2%methionine, 0.2% Tween 20, 0.03% EDTA

TABLE 5 Formulation Composition: 20% PTH, 12.7% HCL RP-HPLC SEC Time PTHPurity [%] Total oxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown(Days) (% RSD) (% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.91 (0.41) 0.22(7.87) 4.40 (1.25) 1.47 (22.55) 0.10 (5.59)  0.00 10 92.55 (0.82) 0.27(7.62) 4.39 (0.88) 2.79 (27.97) 2.27 (66.38) 0.39 24 89.76 (1.09)  0.39(12.76) 4.45 (0.91) 5.41 (18.04) 4.73 (31.30) 1.13 60 85.94 (0.47) 0.38(9.16) 4.19 (1.18) 9.49 (4.39)  6.93 (5.34)  3.22

TABLE 6 Formulation Composition: 20% PTH, 12.7% HCL, 0.01% EDTA RP-HPLCSEC Time PTH Purity [%] Total oxid [%] Isomer [%] Unknown [%]Aggregation [%] Unknown (Days) (% RSD) (% RSD) (% RSD) (% RSD) (% RSD)[%] 0 93.75 (0.13) 0.21 (7.39) 4.33 (1.44) 1.71 (5.00) 0.15 (14.19) 0.0010 93.04 (0.19) 0.25 (4.00) 4.22 (0.96) 2.48 (7.04) 1.59 (15.78) 0.12 2491.51 (0.68)  0.36 (13.89) 4.41 (2.16)  3.72 (15.63) 2.66 (30.89) 0.5260 87.82 (0.70) 0.37 (3.15) 4.04 (3.73) 7.77 (6.35) 5.54 (3.62)  1.97

TABLE 7 Formulation Composition: 20% PTH, 12.7% HCl, 0.01% EDTA, 1%Methionine RP-HPLC SEC Time PTH Purity [%] Total oxid [%] Isomer [%]Unknown [%] Aggregation [%] Unknown (Days) (% RSD) (% RSD) (% RSD) (%RSD) (% RSD) [%] 0 93.77 (0.14) 0.19 (2.99) 4.29 (1.66) 1.75 (3.73) 0.14 (7.14)  0.00 10 92.83 (0.59) 0.51 (9.93) 4.34 (1.80) 2.32 (20.92)2.15 (44.83) 0.32 24 90.69 (0.49)  0.36 (18.73) 4.46 (0.69) 4.49 (9.64) 3.01 (37.35) 0.47 60 90.34 (0.71) 0.36 (6.93)  4.36 (10.62) 4.94 (16.60)3.53 (20.6)  0.79

TABLE 8 Formulation Composition: 20% PTH, 20% Sucrose, 12.7% HCl, 0.2%Tween20, 0.03% EDTA RP-HPLC SEC Time PTH Purity [%] Total oxid [%]Isomer [%] Unknown [%] Aggregation [%] Unknown (Days) (% RSD) (% RSD) (%RSD) (% RSD) (% RSD) [%] 0 93.99 (0.38) 0.45 (2.59) 4.21 (1.35) 1.26(18.38) 0.12 (12.39) 0.00 10 92.98 (0.68)  0.40 (28.67) 4.25 (0.76) 2.38(30.89) 0.40 (98.97) 0.01 24 92.41 (0.06) 0.54 (6.68) 4.54 (0.34) 2.51(1.79)  0.25 (10.58) 0.00 60 91.88 (0.37) 0.57 (1.75) 4.24 (1.43) 3.31(8.41)  0.88 (60.36) 0.00

TABLE 9 Formulation Composition: 20% PTH, 1.2% Tartaric acid, 0.01%EDTA, 1% Methionine, 0.2% Tween20 RP-HPLC SEC Time PTH Purity [%] Totaloxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown (Days) (% RSD)(% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.79 (0.36)  0.44 (11.53) 4.30(0.48) 1.47 (18.95) 0.13 (20.35) 0.00 10 93.50 (0.08) 0.34 (3.36) 4.35(1.09) 1.81 (2.84)   0.62 (131.08) 0.01 24 91.40 (2.04) 0.67 (7.90) 4.34(0.53) 3.60 (53.01) 2.10 (88.57) 0.08 60 90.40 (0.03)  0.66 (10.04) 3.99(2.75) 4.95 (0.77)  3.59 (28.55) 0.33

TABLE 10 Formulation Composition: 20% PTH, 20% Sucrose, 12.7% HCl, 0.2%Tween20, 0.03% EDTA, 2% Methionine RP-HPLC SEC Time PTH Purity [%] Totaloxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown (Days) (% RSD)(% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.92 (0.35) 0.36 (3.24)  4.10(3.51) 1.63 (10.64) 0.15 (10.41) 0.00 10 93.19 (0.67) 0.36 (1.59)  4.32(1.67) 2.13 (26.75)  0.53 (106.67) 0.03 24 92.66 (0.38) 0.40 (15.94)4.55 (3.58) 2.39 (8.32)  0.26 (3.85)  0.02 60 92.64 (0.17) 0.39 (15.80)4.31 (3.04) 2.66 (5.22)  0.49 (48.12) 0.02

TABLE 11 Formulation Composition: 20% PTH, 20% Sucrose, 1.2% Tartaricacid, 0.2% Tween20, 0.03% EDTA, 2% methionine RP-HPLC SEC Time PTHPurity [%] Total oxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown(Days) (% RSD) (% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.48 (0.12) 0.35(11.44) 4.40 (0.47) 1.77 (5.35) 0.12 (9.90)  0.01 10 93.50 (0.08) 0.34(3.36)  4.35 (1.09) 1.81 (2.84)  0.62 (131.08) 0.01 24 92.40 (0.44) 0.37(14.30) 4.65 (2.28)  2.58 (10.62) 0.34 (37.00) 0.01 60 91.83 (0.06) 0.41(5.12)  4.49 (1.48) 3.28 (2.13) 0.36 (29.72) 0.01

TABLE 12 Formulation Composition: 20% PTH, 20% Sucrose, 12.7% HCl, 0.2%Tween20 RP-HPLC SEC Time PTH Purity [%] Total oxid [%] Isomer [%]Unknown [%] Aggregation [%] Unknown (Days) (% RSD) (% RSD) (% RSD) (%RSD) (% RSD) [%] 0 93.76 (0.28) 0.44 (2.27) 4.20 (0.86) 1.60 (13.80)0.14 (4.03)  0.00 10 92.94 (0.29)  0.29 (39.16) 4.21 (1.58) 2.56 (10.80)0.23 (26.45) 0.00 24 92.58 (0.12) 0.45 (3.14) 4.61 (0.92) 2.36 (5.99) 0.51 (46.21) 0.00 60 92.31 (0.05) 0.47 (3.01) 4.19 (1.69) 3.03 (1.40) 0.38 (11.16) 0.00

TABLE 13 Formulation Composition: 20% PTH, 20% Sucrose, 1.2% Glycolicacid, 0.2% Tween 20, 0.03% EDTA, 2% Methionine RP-HPLC SEC Time PTHPurity [%] Total oxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown(Days) (% RSD) (% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.56 (0.12) 0.40(3.79) 4.29 (1.08) 1.74 (4.78)  0.15 (13.33) 0.00 10 93.41 (0.34) 0.42(8.43) 4.28 (0.89) 1.90 (16.54) 0.37 (15.51) 0.00 24 91.95 (0.90) 0.51(6.03) 4.63 (1.14) 2.92 (25.52) 0.48 (42.42) 0.00 60 91.85 (0.54) 0.42(2.73) 4.47 (3.02) 3.25 (16.05) 0.82 (56.11) 0.01

TABLE 14 Formulation Composition: 20% PTH, 20% Sucrose, 1.7% Citricacid, 0.2% Tween20, 0.03% EDTA, 2% Methionine RP-HPLC SEC Time PTHPurity [%] Total oxid [%] Isomer [%] Unknown [%] Aggregation [%] Unknown(Days) (% RSD) (% RSD) (% RSD) (% RSD) (% RSD) [%] 0 93.71 (0.34) 0.37(3.15) 4.22 (1.54) 1.70 (15.28) 0.11 (10.19) 0.00 10 93.63 (0.11)  0.38(14.65) 4.23 (0.36) 1.76 (5.71)  0.22 (19.22) 0.00 24 92.29 (0.21) 0.35(6.66) 4.60 (1.95) 2.76 (3.87)  0.39 (23.47) 0.00 60 90.29 (2.00) 0.33(9.09)  4.48 (11.25) 4.90 (34.30) 2.14 (86.23) 0.68

Example 5

Example 5 demonstrates the utilization of an antioxidant to retardoxidation of hPTH (1-34) agent. Table 15 lists the seven formulationsthat were prepared for the stability study.

TABLE 15 Formulation Formulation Composition (% w/w) A 25% PTH B 25%PTH, 0.5% methionine C 25% PTH, 1% methionine D 25% PTH, 3% methionine E25% PTH, 0.5 mM EDTA F 25% PTH, 1 mM EDTA G 25% PTH, 3 mM EDTA

Table 16 highlights the results of a 3 month stability study. Threepeaks detected by RPHPLC at Relative Retention Times of 0.36, 0.53 and0.68 were attributed to oxidized species of hPTH (1-34) and are denotedOxid 1, 2 and 3, respectively. In all cases, the Oxid 3 species was thepredominant oxidation product.

TABLE 16 Oxidation (%) Oxid 1 Oxid 2 Oxid 3 Total RT = 0.36 RT = 0.56 RT= 0.68 Oxid Time Point 0 Months Formulation Control 0.00 0.14 0.31 0.450.5% Methionine 0.00 0.13 0.28 0.41 1% Methionine 0.00 0.12 0.29 0.41 3%Methionine 0.00 0.12 0.27 0.39 0.5 mM EDTA 0.00 0.12 0.26 0.38 1 mM EDTA0.00 0.14 0.28 0.42 3 mM EDTA 0.00 0.15 0.30 0.45 Time Point 1 MonthsFormulation Control 0.00 0.22 0.46 0.68 0.5% Methionine 0.00 0.24 0.490.73 1% Methionine 0.00 0.20 0.47 0.67 3% Methionine 0.00 0.14 0.36 0.500.5 mM EDTA 0.00 0.13 0.27 0.40 1 mM EDTA 0.00 0.14 0.29 0.43 3 mM EDTA0.00 0.18 0.36 0.54 Time Point 3 Months Formulation Control 0.01 0.330.73 1.06 0.5% Methionine 0.01 0.31 0.67 0.98 1% Methionine 0.02 0.260.61 0.89 3% Methionine 0.00 0.18 0.50 0.68 0.5 mM EDTA 0.00 0.17 0.390.57 1 mM EDTA 0.01 0.17 0.41 0.58 3 mM EDTA 0.01 0.17 0.41 0.59

In summary, the formulation devoid of antioxidants yielded the highestpercentage of total oxidized product and addition of methionine or EDTAretarded oxidation. The results indicate that methionine retardsoxidation in a concentration dependant manner. However, EDTA did notexhibit this phenomenon. Addition of 0.5 mM EDTA to a formulation was aseffective as 3 mM in retarding oxidation. Moreover, the results indicatethat EDTA is more effectual in impeding oxidation than methionine.

These results are graphically illustrated in FIG. 13, which provides thesum of oxidized species of hPTH (1-34).

Example 6

In this example, transdermal delivery of a PTH-based agent using acoated microprojection member was compared to conventional, subcutaneousdelivery of teriparatide PTH (Forteo™). A dose-finding study wasconducted with 10 healthy, young females that received two treatments,separated by at least five days, according to randomly assigned sequenceof 20 μg subcutaneous delivery of Forteo™ and 30 μg transdermal deliveryof a PTH-based agent by coated microprojection. Bioavailability oftransdermally delivered PTH was determined in 20 healthy, young femalesby administering two treatments, separated by at least five day,according to randomly assigned sequence of 40 μg subcutaneous deliveryof Forteo™ and 30 μg transdermal delivery of a PTH-based agent by coatedmicroprojection.

In the dose-finding study, two participants dropped out, eleven subjectsparticipated and eight generated usable data. It was determined thatthree subjects had measurable PTH plasma levels following subcutaneousinjection and eight subjects had measurable PTH plasma levels followingtransdermal delivery. In the bioavailability study, 20 subjectscompleted the study, with 15 subjects demonstrating measurable PTHplasma levels following subcutaneous delivery and 20 subjectsdemonstrating measurable PTH plasma levels following transdermaldelivery.

As shown in FIG. 14, transdermal delivery of a PTH-based agent yieldseffective absorption into the blood stream. FIG. 12 further reflects apreferred pulsatile concentration profile of the PTH agent, i.e., rapidon-set and rapid off-set after reaching Cmax. Further, as shown in FIG.15, the biological activity of PTH following transdermal delivery iscomparable to that following subcutaneous delivery as evidenced byincreased levels of urinary cAMP excretion.

The plasma concentration of PTH following subcutaneous delivery andtransdermal delivery is compared in FIG. 16, which further demonstratesrapid absorption following transdermal delivery. FIG. 16 similarlyreflects a preferred pulsatile concentration profile of the PTH-basedagent, i.e., rapid on-set and rapid off-set after reaching Cmax.

The PK/PD results of the subcutaneous and transdermal delivery arefurther provided in Table 17, which indicate similar bioavailability ofPTH.

TABLE 17 Forteo ™ Subcu- Coated micropro- taneous delivery jectiontransdermal Parameter 40 μg delivery 30 μg P-Value Tmax (hr) 0.58 0.13<0.0001 Cmax (ng/mL)  0.22* 0.32 0.04 AUC 0.75 0.94 0.28 (h · ng/mL) (cv= 152%) (cv = 216%) ΔcAMP (μM) 117 (n = 19) 121 (n = 18) 0.90 p < 0.0001p = 0.0014 *normalized to 30 μg dose

Safety of transdermal delivery was also assessed during this experiment.Generally, transdermal delivery via coated microprojections comparedfavorably to the conventional subcutaneous delivery with similarproportions of subjects reporting adverse effects, but none wereserious. Nausea and vomiting were more common with subcutaneousdelivery.

As will be appreciated by one having ordinary skill in the art, thepresent invention provides numerous advantages. For example, amicroprojection based apparatus and method has the advantage oftransdermal delivery of a PTH-based agent exhibiting a PTH-based agentpharmacokinetic profile similar to that observed following subcutaneousadministration. Another advantage is transdermal delivery of a PTH-basedagent with rapid on-set of biological action. Yet another advantage istransdermal delivery of a PTH-based agent with sustained biologicalaction for a period of up to 8 hours. Further, transdermal delivery froma microprojection array coated with a 10-100 μg dose of teriparatide(hPTH (1-34)) results in a plasma C_(max) of at least 50 pg/mL after oneapplication.

Without departing from the spirit and scope of this invention, one ofordinary skill can make various changes and modifications to theinvention to adapt it to various usages and conditions. As such, thesechanges and modifications are properly, equitably, and intended to be,within the full range of equivalence of the following claims.

1. A method of treating a patient having a bone fracture comprisingadministering a PTH-based agent transdermally to said patient in anamount effective in treating said bone fracture, wherein said method iseffective in treating said bone fracture.
 2. The method of claim 1,wherein treating said bone fracture accelerates bone healing.
 3. Themethod of claim 1, wherein said PTH based agent is transdermallyadministered to said patient comprising the steps of: i) providing adevice comprising a microprojection member having a plurality ofmicroprojections that are adapted to pierce the stratum corneum of thepatient; wherein a biocompatible coating is disposed on saidmicroprojection member, said coating being formed from a coatingformulation comprising at least one PTH-based agent, and ii) applyingsaid microprojection member of said device to a skin site of saidpatient, whereby said plurality of stratum corneum-piercingmicroprotrusions pierce the stratum corneum and deliver said PTH-basedagent to said patient;
 4. The method of claim 3, wherein said coating isdisposed on at least one of said plurality of microprojections
 5. Themethod of claim 3, wherein said PTH based agent is transdermallyadministered to said patient at a dose of approximately 10-1000 μg. 6.The method of claim 5, wherein said dose, when administeredtransdermally to said patient results in a plasma C_(max) of at least 50pg/ml after a single application.
 7. The method of any one of claims 1,2 and 3, wherein said administering of said PTH-based agent to saidpatient exhibits rapid on-set of biological action in said patient andrapid offset after reaching Cmax.
 8. The method of claim 3, wherein thecoating allows for a pulsatile delivery profile having a baseline bloodconcentration in the rage of 50-10000 pg/ml in a period from 1 minute to4 hours.
 9. The method of claim 8, wherein the coating allows for adecrease in blood serum concentration from C_(max) to the baselineconcentration in a period ranging from 1-8 hours after C_(max) isachieved.
 10. The method of claim 9, wherein the C_(max) isapproximately 0.13-0.72 ng/mL.
 11. The method of claim 3, wherein saiddelivered PTH-based agent provides a pharmacokinetic profile similar tothe pharmacokinetic profile provided by subcutaneous administration ofsaid PTH-based agent.
 12. The method of claim 7, wherein a 20 ug bolusdose of said PTH-based agent is transdermally administered in apulsatile fashion comprising applying the microprojection member to askin site of the patient for 15 minutes or less.
 13. The method of claim3, wherein said coating formulation comprises an aqueous formulation.14. The method of claim 3, wherein said coating formulation comprises anon-aqueous formulation.
 15. The method of claim 3, wherein saidPTH-based agent is selected from the group consisting of hPTH (1-34),hPTH salts and analogs, teriparatide and related peptides.
 16. Themethod of claim 15, wherein said hPTH salt is selected from groupconsisting of acetate, propionate, butyrate, pentanoate, hexanoate,heptanoate, levulinate, chloride, bromide, citrate, succinate, maleate,glycolate, gluconate, glucuronate, 3-hydroxyisobutyrate,tricarballylicate, malonate, adipate, citraconate, glutarate, itaconate,mesaconate, citramalate, dimethylolpropinate, tiglicate, glycerate,methacrylate, isocrotonate, β-hydroxibutyrate, crotonate, angelate,hydracrylate, ascorbate, aspartate, glutamate, 2-hydroxyisobutyrate,lactate, malate, pyruvate, fumarate, tartarate, nitrate, phosphate,benzene, sulfonate, methane sulfonate, sulfate and sulfonate.
 17. Themethod of claim 15, wherein said PTH-based agent is recombinant hPTH(1-34) or synthetic hPTH (1-34).
 18. The method of claim 3, wherein saidPTH-based agent comprises in the range of approximately 1-30 wt. % ofsaid coating formulation.
 19. The method of claim 3, wherein thebiocompatible coating comprises 20% PTH, 20% sucrose, 12.7% HCl, 0.2%Tween 20 and 0.03% EDTA.
 20. The method of claim 3, wherein said coatingformulation includes at least one low volatility counterion.
 21. Themethod of claim 20, wherein said PTH-based agent has a positive chargeat said coating formulation pH and said low volatility counterioncomprises a first acid having at least one acidic pKa.
 22. The method ofclaim 21, wherein the amount of said low volatility counterion presentin said coating formulation is sufficient to neutralize the charge ofsaid PTH-based agent.
 23. The method of claim 3, wherein said PTH-basedagent comprises hPTH (1-34) and wherein said coating formulationcomprises at least one viscosity-enhancing counterion.
 24. The method ofclaim 23, wherein said coating formulation has a viscosity in the rangeof approximately 20-200 cp.
 25. The method of claim 3, wherein saidcoating formulation includes a viscosity-enhancing counterion comprisingan acidic counterion.
 26. The method of claim 3, wherein said coatingformulation includes at least one buffer selected from the groupconsisting of ascorbic acid, citric acid, succinic acid, glycolic acid,gluconic acid, glucuronic acid, lactic acid, malic acid, pyruvic acid,tartaric acid, tartronic acid, fumaric acid, maleic acid, phosphoricacid, tricarbally acid, malonic acid, adipic acid, citraconic acid,glutaratic acid, itaconic acid, mesaconic acid, citramalic acid,dimethylopropionic acid, tiglic acid, glyceric acid, methacrylic acid,isocrotonic acid, β-hydroxybutyric acid, crotonic acid, angelic acid,hydracrylic acid, aspartic acid, glutamic acid, glycine, and mixturesthereof.
 27. The method of claim 3, wherein said coating formulationincludes at least one antioxidant selected from the group consisting ofsequestering agents and free radical scavengers.
 28. The method of claim3, wherein said coating formulation includes at least one surfactantselected from the group consisting of sodium lauroamphoacetate, sodiumdodecyl sulfate (SDS), cetylpyridinium chloride (CPC), dodecyltrimethylammonium chloride (TMAC), benzalkonium, chloride, polysorbates, sorbitanderivatives, sorbitan lauratealkoxylated alcohols, polyoxyethylenecastor oil derivatives and mixtures thereof.
 29. The method of claim 3,wherein said coating formulation includes at least one polymericmaterial having amphiphilic properties.
 30. The method of claim 3,wherein said coating formulation includes a hydrophilic polymer selectedfrom the following group consisting of hydroxyethyl starch,carboxymethyl cellulose and salts of, dextran, poly(vinyl alcohol),poly(ethylene oxide), poly(2-hydroxyethyl-methacrylate), poly(n-vinylpyrolidone), polyethylene glycol and mixtures thereof.
 31. The method ofclaim 3, wherein said coating formulation includes a biocompatiblecarrier selected from the group consisting of bioengineered humanalbumin, polyglutamic acid, polyaspartic acid, polyhistidine, pentosanpolysulfate, polyamino acids, sucrose, trehalose, melezitose, raffinose,stachyose and mannitol.
 32. The method of claim 3, wherein said coatingformulation includes a stabilizing agent selected from the groupconsisting of a non-reducing sugar, a polysaccharide and a reducingsugar.
 33. The method of claim 32, wherein said stabilizing agent is anon-reducing sugar.
 34. The method of claim 3, wherein said coatingformulation includes at least one pathway patency modulator selectedfrom the group consisting of osmotic agents, zwitterionic compounds,anti-inflammatory agents and anticoagulants.
 35. The method of claim 3,wherein said microprojection member remains applied to said skin sitefor a period of time in the range of 5 seconds to 24 hours.
 36. Themethod of claim 3, wherein said biocompatible coating comprises aPTH-based agent in the range of approximately 1 ug-1000 ug.
 37. Themethod of claim 3, wherein applying said microprojection membercomprises applying said microprojection member to said skin site with animpact applicator.
 38. The method of claim 3, wherein said delivery ofsaid PTH-based agent exhibits sustained biological action for a periodof up to 8 hours.